[FREELDR]

[FREELDR]
Set BootPartition (DH) to 0xFF in isoboot.S when booting from CD.
Then check for that 0xFF value in FreeLdr to unambiguously detect CD booting instead of using BIOS functions (which don't work reliably on broken BIOSes) or checking for an MBR (which doesn't work on hybrid ISOs).

CORE-12692

svn path=/trunk/; revision=74460