cleaned up function interface to avoid referencing the file system in the worker functions.
replaced StringTable's operators with functions.. The main reason is that these are far easier to look up when browsing the source.
This also fixes a premature translation in SBARINFO that was done in the parsing stage, not the printing stage.
Two files were split:
g_level.h contained both the game data definitions and some prototypes belonging to the game logic. These were split up.
decallib.cpp contained both the data and the animation thinkers. The thinkers are now in their own file.
