Because chanGen() gets called very early, and sometimes it crashes
ScummVM as soon as the game starts. Actually, it's probably enough to
initialise a couple of fields in _tchannel[], but I figured it
couldn't hurt to clear all of _channel[] and _tchannel[].
svn-id: r52741
FR #2813133: "AGI: Proper Tandy 3-Voice/IBM PCjr Sound Support".
Add proper Tandy music. Heavily based on NAGI source, thus attached
its X11 license.
To run it now use -e pcjr. Old one is still default for adlib but
most likely will be changed in the future.
Also lied ground for further separation of different sound generators.
svn-id: r49755
