(re)ntegrate Native MIDI API into NDK - add libamidi

add libamidi to system libs

Bug: 30252756
Bug: 37090545

Test: Build and install NativeMidiTestbed app.
  Run NativMidiTestbed app on DUT.
  Connect to PreSonus AudioBox 22VSL.
  Connect MIDI interface to external MIDI synthesizer. Verify connection.
  Verify MIDI messages sent to external MIDI synthesizer.
  Verify MIDI messages received from external MIDI synthesizer.

Change-Id: Id4bcebbbeb6dc342dbd87b916f1bc78ae32f53db