This significantly speeds up parsing MIDI files with complex
tempo-maps. e.g. "Black MIDI Trilogy_2.mid" has 24134 Tempo
changes. Prior to this commit parsing that file took over 5 minutes.
now it loads in under one seconds (libsmf only; libardour still
add overhead, and now needs about 30-40 seconds, previously
it took about 10 mins).
The problem was that every call to `smf_track_add_event_pulses()`
calls `seconds_from_pulses()` which calls `smf_get_tempo_by_seconds()`
which iterates over the tempo-map:
for every midi-event { for ever tempo until that midi-event {..} }
This does not scale to 3.5M events and 24k tempo-changes.
see also https://github.com/stump/libsmf/pull/7
* Fix validity checks of escaped data
* Handle non-EOT-terminated tracks.
* Fix buffer overflow on tempo change event
* Fix memory leaks in case loading fails
* Fix a logic errors in extract_escaped_event()
* Fix the assertion problem `is_sysex_byte(status)`
* Make libsmf more tolerant to malformed MIDI files.
(fixes import of files generated by NoteEdit)
