Audit mkdir(1)

1) No need for strchr() in mkdirp or a while-loop. Rewrite it in
   a sane and readable way.
2) fix usage according to the manpage.
3) order includes, don't align local variables.
4) argc-style-fix.
5) BUGFIX: Don't try to chmod() *argv when mkdir() / mkdirp() failed.
6) Add newline before return in two places.

README

@@ -44,7 +44,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
 =*  logname         yes                          none
 =   ls              no                           (-C), -S, -f, -m, -s, -x
 =*| md5sum          non-posix                    none
-=*  mkdir           yes                          none
+=*| mkdir           yes                          none
 =*| mkfifo          yes                          none
 =*  mktemp          non-posix                    none
 =*| mv              yes                          none (-i)