Game : moved intermission / level-change stuff --> game.qc
Game : moved CheckHighlightObject --> inventory.qc (the beginnings of
a wider system for handling object interactions....)
Game : removed 'null_entity' -- not needed since gmqcc has a "nil" value.
New code file 'shared/gui.qc' -- empty so far, will contain GUI controls
(buttons, sliders, etc).
Pack-it script : handle the 'shared' and 'dpdefs' directories.