add some mandoc pages and fix some warnings

- add .Os, it is mandatory.
- don't redeclare .Nm when it's not needed.
- fix some warnings (checked with mandoc -Tlint).
- remove some leftover old stuff.

yes.1

@@ -1,10 +1,12 @@
-.TH YES 1 sbase\-VERSION
-.SH NAME
-yes \- output a string repeatedly
-.SH SYNOPSIS
-.B yes
-.RB [ string ... ]
-.SH DESCRIPTION
-.B yes
+.Dd January 30, 2015
+.Dt YES 1 sbase\-VERSION
+.Os
+.Sh NAME
+.Nm yes
+.Nd output a string repeatedly
+.Sh SYNOPSIS
+.Nm
+.Op Ar string ...
+.Sh DESCRIPTION
+.Nm
 will repeatedly output 'y' or the strings specified.
-