Audit cat(1)

1) Fix usage ... spacing
2) use *argv instead of argv[0] in the idiomatic for-loop
3) Stop the naïve usage of "/dev/fd/0" and use plain stdin
   instead (This also makes error-messages more consistent).
4) Add newline before return
5) Remove comma in manpage

cat.1

@@ -1,4 +1,4 @@
-.Dd January 16, 2015
+.Dd March 1, 2015
 .Dt CAT 1
 .Os sbase
 .Sh NAME
@@ -14,7 +14,7 @@ reads each
 .Ar file
 in sequence and writes it to stdout. If no
 .Ar file
-is given,
+is given
 .Nm
 reads from stdin.
 .Sh OPTIONS