vrend: implement polygon stipple by using the system values UBO

Using a texture to emulate the polygon stipple requires a texture and with that a uniform slot in the default UBO. Thus, in order to be exact and account for the possibility that a guest application want's to use polygon stipples, we had to substract "one" from the number of available uniform values in FS. This didn't play well with Tomb Raider 2013 because it results in dropping the number of available uniforms below the number of uniforms required by OpenGL 4.3.

Since the stipple pattern is just a number of bits that need testing it, this emulation can also be implemented by storing the pattern in the system values UBO that is already in use. With that we can drop the reservation of the extra uniform in the FS.

Signed-off-by: Gert Wollny gert.wollny@collabora.com