Enable Background Mode, Set Virtual ports to Enabled.

I have enabled VirtualMidiPorts in this fork. MIDIDestinationCreate fails with a -10844, (kMIDINotPermitted) OSStatus unless you have the audio key set for UIBackgroundModes.

Using TouchOSC, I see both the source and the destination. I know that MIDI Events are being sent, however the callback procs in MidiMonitor are never called.

These changes at least enable the VirtualMidi functionality. Would love to solve this mystery.