glapi: add indexed blend functions (GL 4.0)

This makes some of the UE4 engine demos (Stylized, Mobile Temple)
render correctly, tested on Intel Haswell machine.

Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Acked-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=78716
2 files changed