MD2/MD3 support rewritten + optimizations [by SSNTails]

Backported from Roly Poly Putt, this is my code for a common model format. I also included two loaders, for both MD2 and MD3. This abstracts the rendering code away from the idiosyncrasies of a particular model format, making it a lot easier to add support for others (I also have a non-animated MS3D loader that I may contribute in the future).

This also includes some optimization -- it should now be possible to push a lot more polygons in the renderer itself.

This is the vanilla port of https://git.magicalgirl.moe/KartKrew/Kart-Public/merge_requests/2 with the following changes:

• Fixed VC project files back to XP toolchain and added the new sources to all the projects
• Added new sources to Makefile and CMake
• GCC and Buildbot fixes
  • Unrecognized types, e.g., byte changed to char; bool changed to boolean
  • Mixed D&C - moved variable declarations to top of code blocks
  • Other stuff? I forget.
  • Buildbot results
• ifdef'd some Kart-specific stuff for easier merging
  • USE_FTRANSFORM_MIRROR for encore mirroring
  • USE_FTRANSFORM_ANGLEZ for slope rotation
  • USE_MODEL_NEXTFRAME for nextFrame handling in HWR_DrawMD2(). This was ifdef'd out in Kart, so I made it active again which enables interpolation in DrawModelEx()

See diff vs. SSN's original merge here

Parking this here so we can comment on source lines.