MADS: Initialise _lineIndex

Without this, Rex Nebular crashes on startup for me.
SAGA: Move and rename some defines which are only used in the ITE intro
SAGA: Fix spacing
SAGA: Get rid of the MUSIC_DEFAULT flag
SAGA: Add wrappers for queuing music events
SAGA: Move the ITE intro text together with the other static ITE data
SAGA: Move ITE credits together with the other ITE static data
SAGA: Merge all of the ITE intro cave scene handlers
SAGA: Remove the now unneeded individual cave scene handlers
SAGA: Some renaming
SAGA: Add debug commands for playing music, sounds and voices
SAGA: Cleanup
SAGA: Add support for MIDI music in SAGA2 games