Looks like I overlooked the fact there actually are fix texture combiners,
not just four. The last two texture combiners are easy to miss, because
there are other GPU registers between the first four combiners and the last two.
Upload the configuration register values for the remaining texture combiners to the
shader program's uniforms. This is in preparation for emulating those texture combiners next.
This commit first implements experimental and incomplete
texture combiner support. Currently only the first texture combiner
is implemented. Many sources and combine modes are not implemented yet.
fleroviux