Removed the setNativeMenuBar() call under Qt

I put it there to make the menu usable under Ubuntu 13.10, but since
14.04, this line actually brakes it.

qt/base/result_window.py

@@ -71,7 +71,6 @@ class ResultWindow(QMainWindow):
         
     def _setupMenu(self):
         self.menubar = QMenuBar()
-        self.menubar.setNativeMenuBar(False)
         self.menubar.setGeometry(QRect(0, 0, 630, 22))
         self.menuFile = QMenu(self.menubar)
         self.menuFile.setTitle(tr("File"))