mesa: Add entry for extension ARB_texture_stencil8
V2: Alphabetize the new entry Cc: <mesa-stable@lists.freedesktop.org> Signed-off-by:Anuj Phogat <anuj.phogat@gmail.com> Reviewed-by:
Ian Romanick <ian.d.romanick@intel.com> (cherry picked from commit 340658e4)