Audit mkfifo(1)

1) Fix usage()
2) Group local variables
3) Idiomatic argv-loop
4) BUGFIX: When the m-flag is specified, POSIX clearly says:
   "Set the file permission bits of the newly-created FIFO to the specified mode
   value."
   This means, that if mkfifo() fails for some reason, it should not try to
   chmod() the given path (which has been fixed with the "else if")
   A simple testcase is:

   $ touch testfile; mkfifo -m 000 testfile;

   GNU mkfifo(1): ls -l testfile
   -rw-r--r-- 1 testfile

   sbase mkfifo(1): ls -l testfile
   ---------- 1 testfile
5) Add blank line before return

README

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