MIDI tracks that have no program change events are silent in-game

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If a MIDI track has no program change events, it is intended to be played with instrument 0.
In the M4A engine, until a track reaches a program change event, it will not play any notes.

midi2agb should add in a program change event for instrument 0 so that the GBA engine can begin playing the notes in the track.

Attached is an example MIDI for this situation.
Example.zip