1. Get rid of the evilly bogus strdup(fstab) and free if (fstab == "")
as in umount.
2. Don't use /etc/fstab info if the mount instance does not exactly match
the fstab entry.
3. Reversed the mountpoint checking order in getmntpt().
4. Clarify the "not mounted" error message in mount -u. The previous
"unknown special file or file system" wasn't quite right.
5. Get rid of a 1-byte memory leak; this was reported by jhb.
Submitted by: Martin Blapp <mb@imp.ch>
98683bbf80