Add wxWindowGTK::GTKConnectWidget() helper.

This trivial wrapper function allows to omit "m_widget" and "this" arguments
when calling g_signal_connect().

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62275 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/window.h

@@ -363,6 +363,12 @@ protected:
     // should be called from OnInternalIdle() if it's overridden
     void GTKUpdateCursor();
 
+    // Connect the given function to the specified signal on m_widget.
+    //
+    // This is just a wrapper for g_signal_connect() and returns the handler id
+    // just as it does.
+    gulong GTKConnectWidget(const char *signal, void (*callback)());
+
     // Return true from here if PostCreation() should connect to size_request
     // signal: this is done by default but doesn't work for some native
     // controls which override this function to return false