* Adds USB masquerading according to disk ID in USB part table
* Adds debug feature
* Closes#74 - was due to flags not being properly saved/restored
* Closes#71
* Fixes reentrant INT_13h for some platforms (eg. IBM t43p reenters
INT_13h to issue an SCSI passthrough, AH=0x50)
* Embed MBR as a resource rather than an ms-sys header
* Adds an MBR to prompt the use about USB or HDD boot
* If USB boot is not selected, an INT13h override is added to
make the second bootable drive think it is first (0x81 -> 0x80)
* USB drive BIOS index is left unmodified
Pete Batard