Blender Git Loki

Rename BVMFunction to BVMFunctionBVM in the C API.

The awkward double shorthand "BVM" has two meanings here:
* BVM*** is short prefix for "BlenVM" (to be changed later?).
* ***FunctionBVM means a function in the bvm backend implementation (see FunctionLLVM etc.)

This should be cleaned up later, by chosing a more sensible name for the overall code module.