Fixed cache and MD3 model loading

Also made rd-dedicated buildable again.
Fixed cache loading and model loading.
Fix MD3 model loading, and stubbed entry points

MD3 and MD4 models were incorrectly releasing their file buffers after
loading the files. They are now handled the same way as Ghoul2, where the
buffers are freed later on by the caching system.

A few renderer entry points have also been stubbed out to allow maps to
load.