[Lmuse-user] More monitor on record-arm work

[Tim]

Hello. I have added a 'Monitor' column in the track list.
And some other stuff. In git master now.

I streamlined some of the record-arm and 'bounce'
coding. I tested the 'bounce' features (both Audio Output
record-arm, and Menu -> Bounce to track).

But do give it a thorough workout to make sure I didn't
break anything.

Cheers.
Tim.

ChangeLog:

- Added Monitor track list column.
- Streamlined and tightened up the record-arm and bounce
operations.
- Monitor on record-arm is on by default now, upon first
installation.
- Fixed a problem with arranger track resizing taking much too
long with
many tracks and mixer open - added a separate SC_TRACK_RESIZED.
- Bumped up songfile version to 3.1, so that incompatible
binary header data
can be skipped, since a new Monitor column was added.
Changed other files.