NTSC support.

[tschak909]

Please add support for scrolling the display for NTSC systems.

-Thom

[ch0ccyra1n]

When I get the chance, I'm going to try to change the resolution on my NTSC Amiga to be equivalent to a PAL Amiga's, then running it. If that works, the long-term fix in code would probably be to check resolution and change it to be the correct one at start. I don't imagine this will be an issue unless ProTracker specifically relies on a 50hz refresh rate, which doesn't seem right to me at least. I'll be back later.

-ch0ccyra1n

[ch0ccyra1n]

Related to #6 , hence why I brought it up.