Add example use case to doc

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1465605 13f79535-47bb-0310-9956-ffa450edef68

docs/manual/mod/mod_authz_dbm.xml

@@ -37,7 +37,22 @@
 </summary>
 
 <seealso><directive module="mod_authz_core">Require</directive></seealso>
-
+<section id="examples">
+<title>Example usage</title>
+<p><em>Note that using mod_authz_dbm requires you to require <code>dbm-group</code> 
+instead of <code>group</code>:</em>
+</p>
+<highlight language="config">
+&lt;Directory "/foo/bar"&gt;
+  AuthType Basic 
+  AuthName "Secure Area"
+  AuthBasicProvider dbm 
+  AuthDBMUserFile site/data/users 
+  AuthDBMGroupFile site/data/users 
+  Require dbm-group admin 
+&lt;/Directory&gt;
+</highlight>
+</section>
 <directivesynopsis>
 <name>AuthDBMGroupFile</name>
 <description>Sets the name of the database file containing the list