This brings separate initialization for libcuda and libnvrtc, which
fixes Cycles nvrtc compilation not working on build machines without
CUDA hardware available.
Differential Revision: https://developer.blender.org/D3045
This includes C-API bindings in intern/opensubdiv and CMAke module
which finds the OpenSubdiv library. This filea are not in use so
far, making it a separate commit to make actual integration commit
more clear.
