Prefer shorter results in man page path search

At the moment, manpage search is done using glob.glob, whose ordering is uncertain at best. If we could impose some sorting on the results, it would be more convenient. Now, it's not possible to tell whether manpages.ubuntu.com/foo.1 will send us to foo.1, foo.1posix or foo.1plan9 or something else altogether. If we sorted on length of the result (ascending), `foo.1` will be preferred.