Support as coreboot payload

[XVilka]

Please, add support for building as ELF coreboot payload http://www.coreboot.org/Payloads

[IanSeyler]

Pure64 makes a few BIOS calls when it starts up so it should already work via SeaBIOS (http://www.coreboot.org/SeaBIOS).

If coreboot provides information about CPU topology and memory layout then it could be adjusted to natively support coreboot.

[IanSeyler]

Out of scope for current development.