specs: Add EGL_MESA_device_software

The device extension string is expected to contain the name of the
extension defining what kind of device it is, so the caller can know
what kinds of operations it can perform with it. So that string had
better be non-empty, hence this trivial extension.

v2:
 - drop "fallback", update history and update contributor list

Signed-off-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Mathias Fröhlich <Mathias.Froehlich@web.de>

docs/specs/EGL_MESA_device_software.txt

@@ -0,0 +1,82 @@
+Name
+
+    MESA_device_software
+
+Name Strings
+
+    EGL_MESA_device_software
+
+Contributors
+
+    Adam Jackson <ajax@redhat.com>
+    Emil Velikov <emil.velikov@collabora.com>
+
+Contacts
+
+    Adam Jackson <ajax@redhat.com>
+
+Status
+
+    DRAFT
+
+Version
+
+    Version 2, 2018-10-03
+
+Number
+
+    EGL Extension #TODO
+
+Extension Type
+
+    EGL device extension
+
+Dependencies
+
+    Requires EGL_EXT_device_query.
+
+    This extension is written against the EGL 1.5 Specification.
+
+Overview
+
+    This extension defines a software EGL "device". The device is not backed by
+    any actual device node and simply renders into client memory.
+
+    By defining this as an extension, EGL_EXT_device_enumeration is able to
+    sanely enumerate a software device.
+
+New Types
+
+    None
+
+New Procedures and Functions
+
+    None
+
+New Tokens
+
+    None
+
+Additions to the EGL Specification
+
+    None
+
+New Behavior
+
+    The device list produced by eglQueryDevicesEXT will include a software
+    device. This can be distinguished from other device classes in the usual
+    way by calling eglQueryDeviceStringEXT(EGL_EXTENSIONS) and matching this
+    extension's string in the result.
+
+Issues
+
+    None
+
+Revision History
+
+    Version 2, 2018-10-03 (Emil Velikov)
+        - Drop "fallback" from "software fallback device"
+        - Add Emil Velikov as contributor
+
+    Version 1, 2017-07-06 (Adam Jackson)
+        - Initial version