RunControl: Show correct icon in application output

Add a virtual icon() method to runcontrol.
Actually currently the icon only varies between modes of running.

Task-Nr: QTCREATORBUG-1232

src/plugins/debugger/debuggerrunner.h

@@ -96,6 +96,7 @@ public:
     StopResult stop(); // Called from SnapshotWindow.
     bool isRunning() const;
     QString displayName() const;
+    QIcon icon() const;
 
     void setCustomEnvironment(Utils::Environment env);
     void startFailed();