Add SA-1 rom mapping for SNES

[Silvris]

Might get around to this later myself, but figured opening an issue first would be best.

SA-1 uses an different mapping than the four mappings supported currently (most notably, BWRAM at banks 0x40-0x43), and any pack for an SA-1 game will need access to at least BWRAM (access to WRAM is fishy) for auto-tracking.