Audit chmod(1)

1) Update manpage, refactor the HLP-section and other wordings.
2) BUGFIX: If chmod() fails, don't recurse.
3) Rewrite the arg-loop, fixing several issues:
   BUGFIX: Handle multi-flags (e.g. -RH)
   BUGFIX: Properly handle the termination flag --, error on e.g. --x
   BUGFIX: Error out on an empty flag -.
4) Refactor logic after the arg-loop, which is now simpler thanks
   to argv-incremention.

README

@@ -13,7 +13,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
 =*  cal             yes                          none
 =*| cat             yes                          none
 =*  chgrp           yes                          none
-=*  chmod           yes                          none
+=*| chmod           yes                          none
 =*  chown           yes                          none
 =*| chroot          non-posix                    none
 =*  cksum           yes                          none