beginnings of fancy snippet editing support

src/plugins/texteditor/basetexteditor.h

@@ -482,6 +482,7 @@ public:
         UnusedSymbolSelection,
         FakeVimSelection,
         OtherSelection,
+        SnippetPlaceholderSelection,
         NExtraSelectionKinds
     };
     void setExtraSelections(ExtraSelectionKind kind, const QList<QTextEdit::ExtraSelection> &selections);
@@ -635,6 +636,8 @@ private:
     void showLink(const Link &);
     void clearLink();
 
+    void universalHelper(); // test function for development
+
     // parentheses matcher
 private slots:
     void _q_matchParentheses();