new noise mode for GB

[djmaximum17]

been playing with the Gameboy support and was confused by the note layout. EG c1 to b1 are assigned to frequency register values $F0 to $40 instead of $D7 to $B4. @0 or @1 doesn't change between short and long noise. I created this table with notes from c1 to b5 and registers mapped to note and duty cycle setting.

GB noise note table for next mml2vgm.txt

[kuma4649]

今のところ対応予定は無いです。