Two cd9660 patches

I have posted two patches two the cd9660 fs.

kern/128934 fixes a sign-extension bug that impacts the handling of
	non-GMT dates that are west of GMT.

kern/128942 adds additional tags in the Rock Ridge ER (extension record),
	tags which were defined by the standard fourteen years ago!

Both changes are small and are already included in the other *BSDs and
in Linux, so they should be non-controversial here.

I'm looking for a fs committer to review these, please.  I'd also like
to see them MFC'd to 7-stable.

Thanks.
	-jr