--polyfill {get,set}BootAddress like normal bios does
--they should exist! <https://github.com/MightyPirates/OpenComputers/blob/871e3c83d36c428c8652e0527eb19c217bb072d2/src/main/resources/assets/opencomputers/lua/machine.lua#L1381-L1384>
--normal lua bios says it provides {get,set}BootAddress for "backwards compatibility", but there's no replacement