mesa: Update MESA_INFO to eliminate error

mesa: Update MESA_INFO to eliminate error

If a user set MESA_INFO and the OpenGL application uses a
3.0 or later context then the MESA_INFO debug output will have
an error when it queries for extensions using the deprecated
enum GL_EXTENSIONS. Passing context argument allows code
to return extension list directly regardless of profile.
Commit title updated as recommended by Kenneth Graunke.

Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>