240p Test Suite (NES, GB, GBA) v0.20

I wanted to get a few changes in before the deadline for inclusion on an NES multicart.

Highlights:

• NES, GBA: Add Convergence test
• NES: Add MDFourier tone generator
• GB: Add SGB-only Chroma crosstalk test
• Vertical scroll test (GBA): Display the correct help page
• Help (GB, GBA): Blink Gus's eyes
• Help (GB): Wait to draw status line until Huffman decoding finishes

Behind the scenes:

• GB: Move common routines to RSTs