Added a few #if wxUSE_XXX

Regrouped image format handlers
  Updated the rest accordingly
  Added changes.txt for wxGTK


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@2795 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/combobox.cpp

@@ -104,7 +104,9 @@ bool wxComboBox::Create( wxWindow *parent, wxWindowID id, const wxString& value,
 
     PreCreation( parent, id, pos, size, style, name );
 
+#if wxUSE_VALIDATORS
     SetValidator( validator );
+#endif
 
     m_widget = gtk_combo_new();