MIDI stream processing optimization

[GSoftwareDevelopment]

• Deletion of track status variable (_status)
• The most significant two bits of _trackTime became track status

Cost of cycles for operations:

place	operation	old	new	profit(1)
midi process	Check track stop flag	11	11	0
midi process	Calculate of condition totalTicks>=_trackTime	72	76	-4
midi process	Copy track registers to ZP	129(2)	80(3)	49
track process	Check track stop flag	23	21	2
track process	Jump to jump	27	6	21
track process	End of track (stop flag set)	8	14	-6
midi process	Copy ZP to track registers	137(2)	88(3)	49
		407	296	111

The results are given for the whole operation.

(1) A negative value means a loss (2) in loop (3) unroll loop