gallium: add API for setting window rectangles
Window rectangles apply to all framebuffer operations, either in
inclusive or exclusive mode. They may also be specified as part of a
blit operation.
In exclusive mode, any fragment inside any of the specified rectangles
will be discarded.
In inclusive mode, any fragment outside every rectangle will be
discarded.
The no-op state is to have 0 rectangles in exclusive mode.
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>