Link order was wrong when building via Xcode project because CMake generator sorts files by paths
This made most of classes missing from corresponding segments, and the game crashes right after launch
- added new VARF_Transient flag so that the decision whether to serialize a field does not depend solely on its native status. It may actually make a lot of sense to use the auto-serializer for native fields, too, as this would eliminate a lot of maintenance code.
- defined (u)int8/16 as aliases to the byte and short types (Can't we not just get rid of this naming convention already...?)
- exporting the fields of Actor revealed a few name clashes between them and some global types, so Actor.Sector was renamed to CurSector and Actor.Inventory was renamed to Actor.Inv.
- Member variables are now declared all in one place: InitThingdef(). They
are not partially defined in thingdef_expression.cpp and further refined
in actor.txt.
- This left ParseNativeVariable() parsing only functions, so it has been
renamed to ParseNativeFunction().
- Note that their declarations in InitThingdef() are expected to be
temporary.
