MFC: r344248,r344387

cd9660: dirmatch fails to unmatch when name is prefix for directory record

Loader does fail to properly match the file name in directory record and
does open file based on prefix match.

The cd9660_open() does pass whole path to dirmatch() and we need to
compare only the current path component, not full path.

Additinally, skip over duplicate / (if any) and check if the last component
in the path was meant to be directory (having trailing /). If it is in fact
a file, error out.