Pass built-in array shader inputs in one go

[rdb]

The value for the built-in shader input matrix p3d_TextureMatrix[] is currently specified separately for each element, by incrementing the location index for each array item. As discovered in #846, however, older OpenGL versions do not appear to guarantee that successive elements in uniform arrays use consecutive location indices, and indeed Apple doesn't do this.

There is a hack in place to make this work, but it would be better if the built-in shader input passing system were instead designed to be able to pass in the whole array in one go.

The built-in shader input passing system is very arcane, so it might be worth doing a significant redesign, especially with support for uniform buffers in mind.