Adds an --enable-xcb switch to use XCB in GLX. This only has an effect
when the driver is DRI.

Since the only valid consumer of the DRI drivers is the X.Org xserver,
this changes the default DRI driver directory to match xorg-server:
${libdir}/dri. The old default of /usr/X11R6/modules/dri was wrong for
nearly all current systems.

This commit adds an autoconf macro, MESA_PIC_FLAGS, which sets the
PIC flags according to platform and static/shared setting. The platform
specifics are taken straight from libtool.m4 and stripped down to just
the flags and platforms we cover in Mesa. This should hopefully make it
possible to use autoconf on non-GCC platforms.

The macro is added external to configure.ac in acinclude.m4 since it's
pretty bloated.

Note to BSDers: Previously, x86 defaulted to non-PIC on FreeBSD. I
didn't carry that preference into this macro. Instead, you can just use
--disable-pic where desired.

Minor tweak so that running config.status will entirely recreate the
configure settings by replacing the configs/current symlink.

Two fixes to the asm configuration:
 - Disable when the user is cross-compiling for x86 or x86_64 since it
   requires running an executable compiled for the target host.
 - If the user has specified --enable-32-bit on x86_64 or --enable-64-bit
   on x86, respect that and choose the correct asm architecture.

The DRI modules can only be built against libdrm master (currently
version 2.3.1), so this should be enforced to save people from trying to
build against older versions.

Added a section at the top of the script to consolidate all required
versions.

The variable no_x was being set to yes when libX11 was not found through
pkg-config. This causes AC_PATH_XTRA to skip its search for the X11
libraries, which was not the intended effect. Also switched to using the
PKG_CHECK_EXISTS autoconf macro.

Added the make script version.mk to print the various version numbers
from configs/default. This is used to substitute the version in autoconf
rather than duplicating it in both places.

based on patch by Dan Nicholson <dbn.lists@gmail.com>

Instead of postponing the error from missing pkg-config macros to when
configure is run, make autoconf exit by using m4 macros.

Since the autoconf config inherits from default, we don't need to
duplicate and substitute the MESA_* version numbers in configure.ac.
The version number is only needed in configure for the help text.

The autoconf macro AC_PATH_PROGS handles the case of searching for
multiple program names already, so we don't need to open code it. Also
changed the search to AC_CHECK_PROGS so that it doesn't set the full
path unless the user specified. Finally, report back the found value at
the end for what the user should run.

Add DRI2 direct rendering support to libGL and add DRI2 client side
protocol code.  Extend the GLX 1.3 create drawable functions in
glx_pbuffer.c to call into the DRI driver when possible.

Introduce __DRIconfig, opaque struct that represents a DRI driver
configuration.  Get's rid of the open coded __GLcontextModes in the
DRI driver interface and the context modes create and destroy
functions that the loader was requires to provide.  glcore.h is no
longer part of the DRI driver interface.  The DRI config is GL binding
agnostic, that is, not specific to GLX, EGL or other bindings.

The core API is now also an extension, and the driver exports a list
of extensions as the symbol __driDriverExtensions, which the loader
must dlsym() for.  The list of extension will always include the DRI
core extension, which allows creating and manipulating DRI screens,
drawables and contexts.  The DRI legacy extension, when available,
provides alternative entry points for creating the DRI objects that
work with the XF86DRI infrastructure.

Change DRI2 client code to not use drm drawables or contexts.  We
never used drm_drawable_t's and the only use for drm_context_t was as
a unique identifier when taking the lock.  We now just allocate a
unique lock ID out of the DRILock sarea block.  Once we get rid of the
lock entirely, we can drop this hack.

Change the interface between dri_util.c and the drivers, so that the
drivers now export the DriverAPI struct as driDriverAPI instead of the
InitScreen entry point.  This lets us avoid dlsym()'ing for the DRI2
init screen function to see if DRI2 is supported by the driver.

This logic was copied from the xserver.

Since the xdemos only link to libGL now, we can enable them for all but
the osmesa driver target.

Rather than constructing the GCC include path from `-print-search-dirs',
we can get the path directly from `-print-file-name=include'. This is
used in the Linux kernel build, for example. If no output is returned
from the command, then we don't append a -I path the the makedepend
options.

Also, use -include to avoid error message when make initially fails to
include the non-existent depend file.

The platform-specific overrides to the DRI drivers were being ignored
because the default was being set first. Instead, have the default be a
fallback after the platform checks.

Avoids AVC warnings when allocating executable memory by first checking
if the current process has permission to do so.

This change adds -fno-strict-aliasing when using gcc and g++, just like
the existing configs.

The conditional in src/mesa/Makefile currently hardcodes the cases where
libOSMesa can be built on libGL. Likewise, the xlib case always includes
libOSMesa in the stand-alone target.

This changes the conditional to a loop over the DRIVER_DIRS variable.
This means that any driver configuration can enable or disable osmesa.
The current "stand-alone" rule is changed so that DRIVER_DIRS=x11 and
DRIVER_DIRS="x11 osmesa" are both respected.

The configure option is changed to --enable-gl-osmesa as this change
allows libOSMesa to be built upon any of the libGL-enabling drivers.

Two new configure options to add -m32 or -m64 to the CFLAGS and CXXFLAGS
when GCC is in use. By default, the user supplied options are
environment variables are respected, but these options are quick helps
for the common case of x86/x86_64 using GCC.

Changed the text for the default demos to be "auto" instead of "yes"
since that didn't make much sense in this context. Added an example
value for the --with-dri-drivers option as suggested by Brian.

Point bug reports to Bugzilla like bugs.html. Also, a warning from
autoconf w.r.t. AC_OUTPUT was cleaned up.

Brian suggested that there should be more consistency using xlib vs. x11
in the configure script. Changed the options and variables to suit.

Allow the user to disable use of assembly code through the --disable-asm
option. This is only relevant on the platforms where assembly is
normally enabled such as Linux and FreeBSD.

Report the compiler flags and macros that will be used in the build.
This just provides a quick way to see what configure has silently been
doing.

Allow the user to set the compiler debug flags and macros through the
option --enable-debug. This addes -DDEBUG to the macros and -g to the
CFLAGS and CXXFLAGS if gcc and g++ are in use.

Added a check that PKG_PROG_PKG_CONFIG is defined before calling it so
the user can see a proper error. Without it, the generated configure
script will just pass on to the next statement and bomb with a strange
shell syntax error.

Rather than having the user run `make autoconf' and have the Makefile
setup the configs/current -> autoconf symlink, we can just do that in
configure. This allows the user to just run `make' to build.

Make it clearer what the defaults for the AC_ARG_ENABLE options are and
how to change them.

Sync the default DRI_DIRS with the configs in master. Added some of the
comments from there, too.

Don't link glut with libXt since it's not needed.
(see commit ce98779571)

Report some of the common settings back to the user after configure
has completed.

The user can request specific DRI drivers to build rather than the
default of "all that build on this platform". This allows the list of
drivers to be easily slimmed down.

This is controlled through the option --with-dri-drivers. For example:

    ./configure --with-driver=dri --with-dri-drivers="i965,nouveau"

Unfortunately, using this setting means the DRI drivers aren't filtered
by platform anymore and you might try to build something that doesn't
work.

Allow the user to specify that they want static libraries through the
--{enable,disable}-{static,shared} switches like libtool. The mesa build
only allows for one at a time, so static will be chosen if someone has
passed --enable-static or --disable-shared.

This also allows the mklib options to be set at build time. This allows
-static to be set for mklib, but any platform specific settings are
allowed by setting MKLIB_OPTIONS for configure.

Handling of the program libraries through the APP_LIB_DEPS variable is
pretty ugly, but it seems to work.

The user can request specific demos directories to build in. For
example:

    ./configure --with-demos="demos,xdemos"

The drawback is that we don't check for the necessary libararies in
that case, only that the directory in progs/ exists.

Allow the user to specify channel bits of 16 or 32 to enable OSMesa16 or
OSMesa32 instead of the default OSMesa. This option is controlled
through the option --with-osmesa-bits=BITS and is only honored when the
driver is osmesa.

The osdemos are not enabled in the 16 or 32 bit case because the
Makefile is currently hardcoded to link to -lOSMesa.

Added autoconf support for using OSMesa as the driver instead linking
it to libGL. This is enabled through --with-driver=osmesa.

To differentiate these cases, another option --enable-x11-osmesa is used
to enable or disable building OSMesa when the driver is x11.

Added autoconf bits to allow using DRI as the driver through the option
--with-dri-driver=DRIVER. The options are x11 (default) and dri. Three
DRI specific options for controlling the driver directory, direct
rendering and TLS are also added.

The DRI will probably not work for platforms besides linux and freebsd.