Refactor YieldFor() to avoid code duplication among the ports.

Don't repeat the same code in all the ports, move it to the common base class
and add a new virtual DoYieldFor() for the really port-specific code.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76061 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/unix/evtloop.h

@@ -38,10 +38,10 @@ public:
     virtual int DispatchTimeout(unsigned long timeout);
     virtual void WakeUp();
     virtual bool IsOk() const { return m_dispatcher != NULL; }
-    virtual bool YieldFor(long WXUNUSED(eventsToProcess)) { return true; }
 
 protected:
     virtual void OnNextIteration();
+    virtual void DoYieldFor(long eventsToProcess);
 
 private:
     // pipe used for wake up messages: when a child thread wants to wake up