use exit code 3 for version and help

Plugins which use OK state for help or version information may run
unnoticed in that modes without doing any check. So its good
style to let version and help exit with Unknown state.

Signed-off-by: Sven Nierlein <sven@nierlein.de>

doc/developer-guidelines.sgml

@@ -194,13 +194,15 @@
 					<row>
 						<entry align="center"><para>3</para></entry>
 						<entry valign="middle"><para>Unknown</para></entry>
-						<entry><para>Invalid command line arguments were supplied to the 
+						<entry><para>Invalid command line arguments were supplied to the
 						plugin or low-level failures internal to the plugin (such as unable to fork,
 						or open a tcp socket) that prevent it from performing the specified
 						operation. Higher-level errors (such as name resolution errors,
 						socket timeouts, etc) are outside of the control of plugins and should
 						generally NOT be reported as UNKNOWN states.
-						</para></entry>
+						</para>
+						<para>The --help or --version output should also result in Unknown state.</para>
+						</entry>
 					</row>
 				</tbody>
 			</tgroup>
@@ -610,6 +612,9 @@
 		<para>The option -v or --verbose should be present in all plugins.
 		The user should be allowed to specify -v multiple times to increase
 		the verbosity level, as described in <xref linkend="verboselevels">.</para>
+
+		The exit code for version information or help should be UNKNOWN
+		(3).</para>
     </section>
 
     <section>