meta/blit: Add stencil texturing mode save and restore
v2 (Ken): Only restore the mode if it has changed. Signed-off-by:Topi Pohjolainen <topi.pohjolainen@intel.com> Cc: "10.2" <mesa-stable@lists.freedesktop.org> Reviewed-by:
Kenneth Graunke <kenneth@whitecape.org>