add a suggestion for Redmine administrator on the 500 error page.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@5552 e93f8b46-1217-0410-a6f0-8f06a7374b81

public/500.html

@@ -19,6 +19,7 @@ font-size:0.8em;
   <h1>Internal error</h1>
   <p>An error occurred on the page you were trying to access.<br />
   If you continue to experience problems please contact your Redmine administrator for assistance.</p>
+  <p>If you are the Redmine administrator, check your log files for details about the error.</p>
   <p><a href="javascript:history.back()">Back</a></p>
 </body>
 </html>