Added SetActive to wxEventLoop

Ensured Yield has a wxEventLoop (wxX11)
Process size event explicitly in top-level SetSize (wxX11)
Added wxYield to wxTopLevelWindow::Show (wxX11)


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@14763 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/evtloop.h

@@ -47,6 +47,9 @@ public:
     // return currently active (running) event loop, may be NULL
     static wxEventLoop *GetActive() { return ms_activeLoop; }
 
+    // set currently active (running) event loop
+    static void SetActive(wxEventLoop* loop) { ms_activeLoop = loop; }
+
 protected:
     // the pointer to the port specific implementation class
     class WXDLLEXPORT wxEventLoopImpl *m_impl;