src/usbboot: added in merged 64-bit install image

+ Renamed everything to work generically for both 32 and 64 bit installs
usbboot/Makefile: fixed up real USB test modes

+ added a "real" CDROM mode too (IDE interface is faster than USB?)
usbboot/isolinux.cfg: adding a rescue mode
usbboot/install-ubuntu: recolored
usbboot/dedup-test.py: measure duplication in two files at block-level