Merge branch '4.4' into 5.4

* 4.4:
  Documenting the __root__ section

Author: javiereguiluz

performance.rst

@@ -334,6 +334,14 @@ Sections are a way to split the profile timeline into groups. Example::
     $this->stopwatch->start('processing-file');
     $this->stopwatch->stopSection('parsing');
 
+All events that don't belong to any named section are added to the special section
+called ``__root__``. This way you can get all stopwatch events, even if you don't
+know their names, as follows::
+
+    foreach($this->stopwatch->getSectionEvents('__root__') as $event) {
+        echo (string) $event;
+    }
+
 Learn more
 ----------