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...
LB302: one last fix...
Merge pull request #850 from diizy/lb302

LB302: one last fix...
FxMixer: Fix channel delete
FxMixer: fix crashes on modifying sends
Added a mutex so that the GUI thread can't change the sends around during the rendering loop.