mesa: Remove GL_MESA_resize_buffers

Commit bab755a made the implementation a no-op, and it was only ever
enabled by software rasterizers.

v2: Move the spec into docs/specs/OLD since it's now obsolete
    (squashed patch from Andreas Boll)

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Brian Paul <brianp@vmware.com>
11 files changed