FULLPIPE: Fix off-by-one error when checking valid 'idx'

Verified by sev, but I haven't actually seen it cause any problems.
FULLPIPE: Implement sceneHandler06()
FULLPIPE: Implement scene06_initMumsy()
FULLPIPE: Enable scene06
FULLPIPE: Implement scene06_updateCursor()
TSAGE: R2R - Some more renaming and refactoring in scene 1337
COMMON: Fix mismatched new/delete in the MemoryPool class

Memory is allocated with new in Hashmap::allocNode() and incorrectly
freed with free() in ~MemoryPool() and freeUnusedPages().
Issue reported by Dr. Memory