Modify to output all MIDI tempo events to the first track, since some tools can recognise tempo only in there.

RareSnesSeq: Add workaround for tempo 0.

Known Bugs: DKC2 Bad Bird Rag causes tempo overflow. This happens because Track 3 resets tempo at the beginning, and Track 4 increases the tempo little by little. Since the current VGMTrans do track-by-track conversion, Track 4 causes the overflow. That's shame.