[syslinux] Patch for chain.c32: Set default boot drive to CD drive from which ISOLINUX is booted

[H. Peter Anvin]

Kim Mik wrote:
> Not only grub4dos (grldr) needs the patch to boot correctly after being chainloaded by chain.c32
> when run from ISOLINUX.
> 
> If you want to boot Windows 2000/XP/2003 , from a CD/DVD with ISOLINUX,
> by chainloading SETUPLDR.BIN with chain.c32, chain.c32 needs to pass the
> CD drive from which ISOLINUX was booted as root drive to SETUPLDR.BIN.
> 
> If you want to boot Windows Vista/2008/7, from a CD/DVD with ISOLINUX,
> by chainloading bootmgr with chain.c32, chain.c32 needs to pass the
> CD drive from which ISOLINUX was booted as root drive to bootmgr.

Applied and a build pushed out as 3.83-pre1.

	-hpa