(PS3 Cg) Fixed crash at game start - Cg state was never properly
deinited for PS3 before and we relied on a very dirty hack to set
CgContext to NULL - we can get rid of all that crap now.

PS3 build is now 'fixed' - only thing remaining is that we should
have a mechanism inside the menu to 'reinit' any graphics assets that
were previously set before we lost the state (for instance - RMenu
has one texture image it loads at init_assets time).