make the TMS34010 a bit safer when 8-bit writes are used (Megaphoenix does this..)  I suspect skeetsht will need more improvements along these lines because it's hooked up to an 8-bit CPU?

This at least means we don't have to overclock the 68k by a silly amount on on megaphx, and fixes round 4, although it doesn't fix all the graphic corruption, of note round 6.