[ticket/13716] Check phpBB version against config version

Display a warning in the ACP if the version constant (files)
does not match the phpbb_config version
(often indicating that the database updates hasn't been run)

PHPBB3-13716

phpBB/includes/acp/acp_main.php

@@ -453,6 +453,12 @@ class acp_main
 			$template->assign_var('S_VERSION_UP_TO_DATE', true);
 		}
 
+		// Incomplete update?
+		if (phpbb_version_compare($config['version'], PHPBB_VERSION, '<'))
+		{
+			$template->assign_var('S_UPDATE_INCOMPLETE', true);
+		}
+
 		/**
 		* Notice admin
 		*