Correctly apply CurVol setting in ~/.xtimidity

Correctly apply CurVol setting in ~/.xtimidity

Make the player correctly apply CurVol setting in ~/.xtimidity (timidity
ignores RC_CHANGE_VOLUME when not playing, so do it more directly) (all
issues except the first existed in the original 2.13.2 interface).

Also fix:
-Make the check mark disappear also the first time trace is unhidden
-Do not allow the playbutton to activate when no files are loaded

This should do for 2.14.0.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>