Two-note Arpeggio for effect 00xy

[Toonlink8101]

I'm not sure if this would conflict with Deflemask compatibility, but it would be necessary for Famitracker compataility (#478).

In Famitracker, arpeggio effect commands can either have three notes or two notes. If y is 0, the note arpeggiates between the base note and the note x semi-tones above.

Deflemask compatibility might be maintained by converting commands ending in 0 to start with 0. This would be in line with Famitracker as well. For example, a dmf file with the command 0070 would be converted to 0007.

This would allow for both two-note and three-note arpeggios without having multiple instruments dedicated to each two-note arp.