- Separate SMF::open and SMF::create, more powerful interface for both.
- Correctly handle note ons with velocity 0 as note offs in sequence.
- Use SMF (i.e. libsmf) for MIDI import
git-svn-id: svn://localhost/ardour2/branches/3.0@4558 d708f5d6-7413-0410-9779-e7cbd77b26cf