MaxVertexBlendMatrices, multi-matrix vertex blending and D3DX

[Stefan Dösinger]

> The only other option I'm aware of is to await the shader-based fixed
> function pipeline replacement which might contain an implementation of
> the D3DRS_VERTEXBLEND renderstates.
I worked on a pipeline replacement using GL_ARB_vertex_program a few months
ago but hit some roadblocks, so I never finished it. The main problem was
that the performance was awful. Even in apps like 3Dmark 2000, which are hit
rather badly by drawStridedSlow it resulted in a net slowdown. I am pretty
sure my code can be optimized(the lighting code is *awful*), but it
certainly complicates things if I have to be really picky wrt performance
from the start to avoid causing regressions.