avoid creating expensive stacktrace in dbg_deprecated()

now the method is aborting early again unless the data is actually used

inc/infoutils.php

@@ -441,8 +441,16 @@ function dbglog($msg,$header=''){
  * Log accesses to deprecated fucntions to the debug log
  *
  * @param string $alternative The function or method that should be used instead
+ * @triggers INFO_DEPRECATION_LOG
  */
 function dbg_deprecated($alternative = '') {
+    global $conf;
+    global $EVENT_HANDLER;
+    if(!$conf['allowdebug'] && !$EVENT_HANDLER->hasHandlerForEvent('INFO_DEPRECATION_LOG')) {
+        // avoid any work if no one cares
+        return;
+    }
+
     $backtrace = debug_backtrace();
     array_shift($backtrace);
     $self = $backtrace[0];