IEditor: Make duplicatesSupported a value member

Change-Id: Iee75dd4155d5074bb319df79d006b6d5e2989e14
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/texteditor/snippets/snippeteditor.h

@@ -48,7 +48,6 @@ class TEXTEDITOR_EXPORT SnippetEditor : public BaseTextEditor
 public:
     SnippetEditor(SnippetEditorWidget *editorWidget);
 
-    bool duplicateSupported() const { return false; }
     Core::IEditor *duplicate() { return 0; }
 };