make user-config-readonly explicit when writing to config.

src/etc/inc/config.lib.inc

@@ -153,6 +153,8 @@ function write_config($desc = 'Unknown', $backup = true)
 			$user = getUserEntry($_SESSION['Username']);
 			if (is_array($user) && userHasPrivilege($user, "user-config-readonly")) {
 				session_write_close();
+				// okay, it's not very nice to check permissions here, but let's make it explicit while we do...
+				log_error(gettext("WARNING: User")." ".$_SESSION['Username']." ".gettext("may not write config (user-config-readonly set)"));
 				return false;
 			}
 		}