Remove old (already #if 0'ed) implementation of Evoral::coverage() and its
comments.
Tidy up the comment enumerating all the possible ways in which two ranges
can overlap, note the Evoral::OverlapType corresponding to each one, and add
comments to the if()s in coverage corresponding to the cases in the list of
overlap types.
Remove some commented-out assert()s that actually do happen, and re-instate
one that really shouldn't.
Fix a small typo (with -> within)
Colin Fletcher
43cc295a58