Introduced a QML-specific debugger tool bar

This one has the common debugger actions as well as the QML Observer
specific part. This makes sure those actions are generally available and
not only from the QML Observer dock widget.

The filter in the tool bar should still be moved back.

Reviewed-by: Christiaan Janssen <christiaan.janssen@nokia.com>

src/plugins/debugger/debuggerplugin.h

@@ -38,6 +38,8 @@
 
 #include <extensionsystem/iplugin.h>
 
+QT_FORWARD_DECLARE_CLASS(QAction)
+
 namespace ProjectExplorer {
 class RunConfiguration;
 class RunControl;
@@ -65,6 +67,7 @@ public:
     // Used by QmlJSInspector.
     static bool isActiveDebugLanguage(int language);
     static DebuggerMainWindow *mainWindow();
+    static QAction *visibleDebugAction();
 
 private:
     // IPlugin implementation.