Don't install idle event handler in secondary threads.

I've not seen this happen yet, but it can, and I'm taking this precaution.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@22625 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/cocoa/app.h

@@ -34,6 +34,7 @@ public:
     inline void CocoaRequestIdle() { m_isIdle = true; }
 protected:
     WX_NSApplication m_cocoaApp;
+    WX_NSThread m_cocoaMainThread;
     void CocoaInstallIdleHandler();
     bool m_isIdle;