$A130xx area usage

The $A13000 to $A130FF address range is special in that the /TIME signal on the cartridge slot is asserted whenever the 68000 accesses it (simplifying the wiring for extra on-cartridge hardware). However it's a limited range, so we want to make sure to avoid stepping on each other.

List of already used `$A130xx` addresses
Addresses	Used by
`$A13000` to `$A1300F`	Private use
`$A130C0` to `$A130CF`	Mega Wifi
`$A130D0` to `$A130E7`	Mega Everdrive
`$A130EC` to `$A130EF`	32X signature
`$A130F0` to `$A130FF`	Sega mapper

Pier Solar uses the $A13000 to $A1300F region for its custom mapper and EEPROM access. It wouldn't be recommended to put anything there that you want to be usable across multiple games.

$A130E8 is being eyed for potential standarization on EEPROM use.