Linup API of wxRadioBox::Show on all ports. Move wxRadioBox::IsValid from wxUniversal to base class (+ GTK which do not use base class) and use it where applicable. Minor source cleaning.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@32329 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/palmos/radiobox.cpp

@@ -354,12 +354,15 @@ bool wxRadioBox::Enable(int item, bool enable)
 
 bool wxRadioBox::Show(bool show)
 {
+    // TODO
     return false;
 }
 
 // Show a specific button
-void wxRadioBox::Show(int item, bool show)
+bool wxRadioBox::Show(int item, bool show)
 {
+    // TODO
+    return false;
 }
 
 wxString wxRadioBox::GetLabel()