Rewrite page(2) references to page(3).

Add description of new libmach.

man/man3/auth.3

@@ -120,7 +120,7 @@ It should be used instead of
 .I mount
 whenever the file server being mounted requires authentication.
 See
-.IR bind (2)
+.IR bind (3)
 for a definition of the arguments to
 .I mount
 and
@@ -196,7 +196,7 @@ file used is
 An
 .B sprint
 (see
-.IR print (2))
+.IR print (3))
 of 
 .I fmt
 and the variable arg list yields a key template (see
@@ -388,8 +388,8 @@ frees a challenge/response state.
 .B /sys/src/libauth
 .SH SEE ALSO
 .IR factotum (4),
-.IR authsrv (2),
-.IR bind (2)
+.IR authsrv (3),
+.IR bind (3)
 .SH DIAGNOSTICS
 These routines set
 .IR errstr .