Viper updater

[9ary]

This requires setting the extended and command mode bits in the header, and writing our own flashing code.

The Viper design uses a stupid 4 wire install, which means it doesn't have DO and CS lines hooked up, so it is crucial that nothing touches EXI channel 0 until we're done with it. This means no SRAM, no SP1 and no card slot A.

This is most likely not happening until I get my hands on a Viper.