1. Fixed a bug where trying to edit the envelope of a stereo pair
where only one of the two channels is visible would crash. (This was
introduced by the WaveClip code, because it's possible that one track
has a clip there and the other doesn't...in addition to checking for
this case, to make the envelope work properly too, both in a stereo
pair must be drawn even if only one is visible.)
2. Opening or importing multiple files now loads the filenames in
sorted order. It was annoying me to drag Track1.wav ... Track8.wav
to Audacity and having them import in some completely random order
every time (on the Mac).
3. Collapsing or expanding a track ('minimizing', internally in the
code) now adjusts the vertical scroll bar, as it should.