Don't include the lazy precompiled.h everywhere, only what's
required for the compilation unit.
platform.h needs to be included instead to provide all essential
defines and types.
All includes use the relative path to the neo or the game
specific root.
Move all idlib related includes from idlib/Lib.h to precompiled.h.
precompiled.h still exists for the MFC stuff in tools/.
Add some missing header guards.
variable set but not used
Removes some CollisionModel code under _DEBUG which was probably a
leftover, since it was completely useless (its done later anyways).
The unused WriteLossless() was using libjpeg internals found in
jpegint.h. This header is available with libjpeg8, but not shipped
by most distros. Disable the relevant code - no functional
changes.
