Do not realize the top level shell that acts as a parent

for top level windows. Add a realized child for the shell
for functions requiring it (clipboard at the moment).
  Use XtPopup to show top level widgets, as per Motif
guidelines.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@27397 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/motif/dialog.cpp

@@ -291,8 +291,8 @@ void wxDialog::SetTitle(const wxString& title)
 
 bool wxDialog::Show( bool show )
 {
-    if( !wxTopLevelWindowMotif::Show( show ) )
-        return FALSE;
+    if( !wxWindowBase::Show( show ) )
+        return false;
 
     m_isShown = show;