MMC1 32K banking

[mysterymath]

Now that the LMAs and VMAs have been reworked in the NES targets, it should be possible to directly support MMC1's 32KiB banking mode. The approaches used should also be generally applicable to other mappers without a fixed PRG-ROM bank, which improves the generality of the SDK.

[mysterymath]

Downgrading to p2 now that there's a known way to do this.