v1.55

mb-audit: (v1.55)

• [#25] Improve AY Registers dump on failure.

music test (v1.3):

• Visually show when an AY chip is active (INVERSE) or muted (NORMAL).
• [#26] Playback routine will use 6522-B's Timer1 if 6522-A isn't detected.
• [#18] Fix for detecting //c (required for MB4c support).