mesa: Disable GL_EXT_framebuffer_object in core profiles and OpenGL 3.1

mesa: Disable GL_EXT_framebuffer_object in core profiles and OpenGL 3.1

GL_EXT_framebuffer_object differs from GL_ARB_framebuffer_object in ways
that we can't and don't implement in core profiles.  Exposing it is a
lie, so we shouldn't do that.

It's possible the some other GL_EXT_framebuffer_* extensions should be
disabled, but it's not quite so clear cut.

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