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

include/wx/univ/radiobox.h

@@ -96,7 +96,7 @@ public:
     virtual void SetString(int n, const wxString& label);
 
     virtual bool Enable(int n, bool enable = true);
-    virtual void Show(int n, bool show = true);
+    virtual bool Show(int n, bool show = true);
 
     // we also override the wxControl methods to avoid virtual function hiding
     virtual bool Enable(bool enable = true);
@@ -132,9 +132,6 @@ protected:
     // common part of all ctors
     void Init();
 
-    // check that the index is valid
-    bool IsValid(int n) const { return n >= 0 && n < GetCount(); }
-
     // sets m_majorDim and calculate m_numCols and m_numRows
     void SetMajorDim(int majorDim);