like the dhewm3 version and the OS and architecture of the dhewm3
version that created the savegame.
Also added an internalSavegameVersion so be independent of BUILD_NUMBER
fixes#344
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.
