Monsters got stuck in same places of d3xp because PVS calculations
returned that they were not in the players PVS.
This only happened on LP64 systems like Unix/Linux amd64 where
sizeof(long) == 8 - it did not happen on Win64 because it's LLP64, i.e.
sizeof(long) == 4 (like on x86 32bit).
Bit fiddling code in Pvs.cpp seemed to assume that sizeof(long) == 4
like on win32.
Fixes#7.
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.
