egl: Enable EGL_EXT_client_extensions

Insert two fields into _egl_global to hold the client extensions and
statically initialize them:
    ClientExtensions // a struct of bools
    ClientExtensionString

Post-patch, Mesa supports exactly one client extension,
EGL_EXT_client_extensions.

Signed-off-by: Chad Versace <chad.versace@linux.intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/egl/main/eglapi.c

@@ -87,6 +87,7 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "eglglobals.h"
 #include "eglcontext.h"
 #include "egldisplay.h"
 #include "egltypedefs.h"
@@ -354,10 +355,15 @@ eglTerminate(EGLDisplay dpy)
 const char * EGLAPIENTRY
 eglQueryString(EGLDisplay dpy, EGLint name)
 {
-   _EGLDisplay *disp = _eglLockDisplay(dpy);
+   _EGLDisplay *disp;
    _EGLDriver *drv;
    const char *ret;
 
+   if (dpy == EGL_NO_DISPLAY && name == EGL_EXTENSIONS) {
+      RETURN_EGL_SUCCESS(NULL, _eglGlobal.ClientExtensionString);
+   }
+
+   disp = _eglLockDisplay(dpy);
    _EGL_CHECK_DISPLAY(disp, NULL, drv);
    ret = drv->API.QueryString(drv, disp, name);
 

src/egl/main/eglglobals.c

@@ -47,6 +47,14 @@ struct _egl_global _eglGlobal =
       _eglUnloadDrivers, /* always called last */
       _eglFiniDisplay
    },
+
+   /* ClientExtensions */
+   {
+      true /* EGL_EXT_client_extensions */
+   },
+
+   /* ClientExtensionsString */
+   "EGL_EXT_client_extensions"
 };
 
 

src/egl/main/eglglobals.h

@@ -31,6 +31,7 @@
 #ifndef EGLGLOBALS_INCLUDED
 #define EGLGLOBALS_INCLUDED
 
+#include <stdbool.h>
 
 #include "egltypedefs.h"
 #include "eglmutex.h"
@@ -48,6 +49,12 @@ struct _egl_global
 
    EGLint NumAtExitCalls;
    void (*AtExitCalls[10])(void);
+
+   struct _egl_client_extensions {
+      bool EXT_client_extensions;
+   } ClientExtensions;
+
+   const char *ClientExtensionString;
 };