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.

unlink.1

@@ -1,16 +1,17 @@
-.TH UNLINK 1 sbase\-VERSION
-.SH NAME
-unlink \- call the unlink function
-.SH SYNOPSIS
-.B unlink
-.RB file
-.SH DESCRIPTION
-.B unlink
+.Dd January 30, 2015
+.Dt UNLINK 1 sbase\-VERSION
+.Os
+.Sh NAME
+.Nm unlink
+.Nd call the unlink function
+.Sh SYNOPSIS
+.Nm
+.Ar file
+.Sh DESCRIPTION
+.Nm
 calls the
-.IR unlink
+.Xr unlink 2
 function on
-.IR file.
-
-
-.SH SEE ALSO
-.IR unlink (2)
+.Ar file.
+.Sh SEE ALSO
+.Xr unlink 2