This more-or-less gets rid of the shadow system's only depencency on FFP
stuff. All that remains is it using OSG cameras, which OSG provides a
uniform-based implementation of, too, which we can trivially migrate to.
This should mean we're not eating any of the ~8 FPP-friendly texture
units, which is good as Morrowind models can use all of those on their
(although they very rarely do), and instead use some of the ~160
shader-only texture image units. This just requires not calling
glEnable(GL_TEXTURE_2D), accomplished by changing
setTextureAttributeAndModes to setTextureAttribute.
Also changes from using glTexGen and its eye plane matrices to pass the
shadow space matrix for each light to explicit uniforms. Thankfully, the
maths was a simple combination of the valid region matrix and eye plane
matrix maths.
As of this commit, I believe this kills shadows in one eye for stereo
rendering.
