Add precomp.h to MSBuild filters.
Use vsnprintf instead of vsprintf in 2d\font.cpp
Flesh out the Win32 precompiled header some more.
Add obnoxious typedef and cast for PhysFS integer truncation.

- This does not fix the fact that the code completely falls over
  on file with greater than 31 significant bits of length.  But it
  at least makes the scope of the problem somewhat identifiable by
  searching and it stops a huge number of warnings from being
  generated all over.