More precision regarding the openlog(3) *ident argument;

direction suggested by Laurence Tratt <laurie at tratt dot net>,
part of the wording from deraadt@.
While here, add the missing STANDARDS section, correct HISTORY,
drop redundant verbiage from RETURN VALUES, and garbage collect .Tn.
OK sthen@ jmc@ millert@ and Laurence Tratt,
and deraadt@ likes one line of the patch in particular.

lib/libc/gen/syslog.3

@@ -1,4 +1,4 @@
-.\"	$OpenBSD: syslog.3,v 1.35 2019/08/30 20:27:25 jmc Exp $
+.\"	$OpenBSD: syslog.3,v 1.36 2020/02/05 12:35:19 schwarze Exp $
 .\"
 .\" Copyright (c) 1985, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -27,7 +27,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: August 30 2019 $
+.Dd $Mdocdate: February 5 2020 $
 .Dt SYSLOG 3
 .Os
 .Sh NAME
@@ -216,12 +216,17 @@ and
 .Fn vsyslog .
 The parameter
 .Fa ident
-is a string that will be prepended to every message.
+points to a string that will be prepended to every message;
+its storage must persist until
+.Fn closelog
+or the corresponding
+.Fn closelog_r .
+If the content of the string is changed, behaviour is unspecified.
+.Pp
 The
 .Fa logopt
 argument
-is a bit field specifying logging options, which is formed by
-.Tn OR Ns 'ing
+is a bit field specifying logging options, which is formed by OR'ing
 one or more of the following values:
 .Bl -tag -width LOG_AUTHPRIV
 .It Dv LOG_CONS
@@ -310,18 +315,6 @@ It takes an additional pointer to a
 .Fa syslog_data
 structure.
 .Sh RETURN VALUES
-The
-.Fn closelog ,
-.Fn closelog_r ,
-.Fn openlog ,
-.Fn openlog_r ,
-.Fn syslog ,
-.Fn syslog_r ,
-.Fn vsyslog ,
-and
-.Fn vsyslog_r
-functions return no value.
-.Pp
 The routines
 .Fn setlogmask
 and
@@ -349,11 +342,58 @@ syslog_r(LOG_INFO|LOG_LOCAL2, &sdata, "foobar error: %m");
 .Sh SEE ALSO
 .Xr logger 1 ,
 .Xr syslogd 8
+.Sh STANDARDS
+The functions
+.Fn syslog ,
+.Fn openlog ,
+.Fn closelog ,
+and
+.Fn setlogmask
+conform to the X/Open Systems Interfaces option of
+.St -p1003.1-2008 .
+.Pp
+The facilities
+.Dv LOG_AUTHPRIV ,
+.Dv LOG_FTP ,
+and
+.Dv LOG_SYSLOG ,
+the option
+.Dv LOG_PERROR ,
+and the macro
+.Fn LOG_UPTO
+are extensions to that standard.
+.Pp
+The standard option
+.Dv LOG_NOWAIT
+is deprecated in
+.Ox
+and has no effect.
 .Sh HISTORY
-These
-functions appeared in
-.Bx 4.2 .
-The reentrant functions appeared in
+The functions
+.Fn syslog ,
+.Fn openlog ,
+and
+.Fn closelog
+appeared in
+.Bx 4.2 ,
+.Fn setlogmask
+in
+.Bx 4.3 ,
+and
+.Fn vsyslog
+in
+.Bx 4.3 Net/1 .
+.Pp
+The functions
+.Fn syslog_r ,
+.Fn vsyslog_r ,
+.Fn openlog_r ,
+.Fn closelog_r ,
+and
+.Fn setlogmask_r
+appeared in
+.Bx 386 0.1
+and have been available since
 .Ox 3.1 .
 .Sh CAVEATS
 It is important never to pass a string with user-supplied data as a