add a man page for suser() because its usage is not as obvious

as you would first think.

share/man/man9/suser.9

@@ -0,0 +1,69 @@
+.\"
+.\" Copyright (c) 1996 Julian R Elischer
+.\" All rights reserved.
+.\"
+.\" This code is derived from software contributed by Kenneth Stailey.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\"    must display the following acknowledgement:
+.\"	This product includes software developed for the FreeBSD Project
+.\"	by Julian R Elischer
+.\" 4. The name of the author may not be used to endorse or promote products
+.\"    derived from this software without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.Dd Oct 15, 1996
+.Dt SUSER 9
+.Os FreeBSD
+.Sh NAME
+.Nm suser
+.Nd check if we are superuser and note
+.Sh SYNOPSIS
+.Fd #include <sys/ucred.h>
+.Ft int
+.Fn suser "struct ucred *cred, u_short *acflag"
+.Sh DESCRIPTION
+The
+.Nm
+function checks if the credentials given include superuser powers.
+.Pp
+The
+.Nm
+routine notes the fact that superuser powers have been used in the 
+word pointed to by the second argument which should be a pointer to
+the p_acflags word of the proc structure. If the second argument is NULL
+then the usage is not noted.  Because part of it's function is to notice
+whether super powers have been used, 
+.Nm 
+should be called after other permission possibilities have been exhausted.
+
+
+.Sh RETURN VALUES
+The
+.Nm
+function returns 0 if the user has super powers and EPERM otherwise.
+This is the
+.Em reverse logic
+of some other implimentations of
+.Nm
+in which a TRUE response indicates Super powers.
+