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@32325 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/radiobox.h

@@ -33,7 +33,7 @@ class WXDLLEXPORT wxRadioBoxBase : public wxItemContainerImmutable
 public:
     // change the individual radio button state
     virtual bool Enable(int n, bool enable = true) = 0;
-    virtual void Show(int n, bool show = true) = 0;
+    virtual bool Show(int n, bool show = true) = 0;
 
     // layout parameters
     virtual int GetColumnCount() const = 0;