A fix to IPH waiting code: don't wait for already finished notes, plus a bit of optimization
Merge pull request #849 from diizy/mixeriph2

A fix to IPH waiting code: don't wait for already finished notes, plus a...
3-in-1 bugfix special
Fixes bugs: #568, #289 and the incorrect timing for midi-noteoffs (see mailing list)
Further safeguards needed...
Make that 4: Fix stuck midi notes on changing master pitch
5th: fix #563 - do not destroy IPH's on "All Notes Off" MIDI commands