Allow navigating into/from children with arrow keys

Related to merge request #106: Jump to filename if Key_Left pressed on
result string in SearchResultWindow.

Reviewed-by: Daniel Molkentin <daniel.molkentin@nokia.com>

src/plugins/coreplugin/manhattanstyle.cpp

@@ -407,6 +407,9 @@ int ManhattanStyle::styleHint(StyleHint hint, const QStyleOption *option, const
         if (panelWidget(widget))
             ret = false;
         break;
+    case QStyle::SH_ItemView_ArrowKeysNavigateIntoChildren:
+        ret = true;
+        break;
     default:
         break;
     }