Added more utility functions to cCuboid.

GetVolume(), Expand(), ClampX(), ClampY(), ClampZ()
APIDump: Separated out Geometry-related classes to their own file.
APIDump: Documented new cCuboid functions.
APIDump: Added Geometry file to project.
Attempted fix for several GCC warnings.
Fixed a gcc warning in FastNBT.h.
Fixed crash and some warnings in map handling.

Fixes #728.