SCUMM: Add support for Steam versions of Indy 3, Indy 4, Loom and Dig

Many Thanks to Ben Castricum for the original patch
SCUMM: Add support for CD audio tracks in the Steam versions of Loom

Many Thanks to Ben Castricum for the original patch
Merge pull request #470 from bluegr/Lucasarts_Steam

SCUMM: Add support for Steam versions of Indy 3, Indy 4, Loom and Dig