Back port of wxSocket-related fixes from trunk.

This patch combines the changes from the following trunk revisions:
 - r61675
 - r61676
 - r61677
 - r61678
 - r61685
 - r61686
 - r61687
 - r61688
 - r61689
 - r61690
 - r61696
 - r61726

It refactors wxSocketImpl creation to use a Mac-specific version of it in GUI
Mac applications which fixes generation of socket events under Mac (see #11030)
and also fixes bug in wxSocketServer::WaitForAccept() (see #11107).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_9_0_BRANCH@61734 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/private/fdiodispatcher.h

@@ -12,23 +12,7 @@
 #define _WX_PRIVATE_FDIODISPATCHER_H_
 
 #include "wx/hashmap.h"
-
-// handler used to process events on descriptors
-class wxFDIOHandler
-{
-public:
-    // called when descriptor is available for non-blocking read
-    virtual void OnReadWaiting() = 0;
-
-    // called when descriptor is available  for non-blocking write
-    virtual void OnWriteWaiting() = 0;
-
-    // called when there is exception on descriptor
-    virtual void OnExceptionWaiting() = 0;
-
-    // virtual dtor for the base class
-    virtual ~wxFDIOHandler() { }
-};
+#include "wx/private/fdiohandler.h"
 
 // those flags describes sets where descriptor should be added
 enum wxFDIODispatcherEntryFlags