[syslinux] chain.c32: hiding partitions

[H. Peter Anvin]

Hi all,

I have added a "hide" command to chain.c32; this hides any *primary* 
partitions on the drive with a DOS, OS/2 or Win32 partition type by 
adding 0x10 to the partition type, and the reverse for the partition 
being booted.

I currently do not modify logical partitions.

I would have made this a prerelease, except I can't get to my build 
machine at the moment.  However, if this is relevant functionality for 
you and you can build syslinux from git, you may want to test it out.

NOTE: this *does* write to the disk, so you may want to smoke-test it on 
a box you don't care about if you lose data...

	-hpa