glsl: add lowering passes for carry/borrow

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Matt Turner <mattst88@gmail.com>
mesa/st: enable carry/borrow lowering pass

This handles the last of the ARB_gs5 instructions currently present in
mesa.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nvc0: treat non-linear 2DRect textures the same as 2D

This fixes textureGather(2DRect) piglit tests, and does not appear to
have any adverse effects.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nouveau: remove cb_dirty, it's never used

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nouveau: add ARB_buffer_storage support

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
docs: update ARB_buffer_storage for nouveau