[Grml] Chainboot Cheatcode

[Mark]

Older PCs do not have BIOS support for USB boot.  Some offer USB boot,
but it just doesn't work.  Some machines only have USB support by means
of PCI or ISA cards, and these cannot be booted.

All these machines will boot GRML off CD.  So, the idea is this - offer
a cheatcode to transfer control to a USB/Firewire/SCSI drive.  This is
not the same thing as using a /home directory on the drive, it means
complete Linux system transfer.
Mark