Editor: Refactor Open Link in Next Split.

Cleanup code and added shortcuts and menu entries for
- open header/source in next split
- follow symbol under cursor in next split
- open declaration/definition in next split

Change-Id: I2c4347749d26669d88b7c2968f30f60710f442b1
Reviewed-by: Petar Perisin <petar.perisin@gmail.com>
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>

src/plugins/texteditor/texteditoractionhandler.h

@@ -141,6 +141,7 @@ private slots:
     void indent();
     void unindent();
     void openLinkUnderCursor();
+    void openLinkUnderCursorInNextSplit();
 
     void gotoLineStart();
     void gotoLineStartWithSelection();
@@ -213,7 +214,9 @@ private:
     QAction *m_indentAction;
     QAction *m_unindentAction;
     QAction *m_followSymbolAction;
+    QAction *m_followSymbolInNextSplitAction;
     QAction *m_jumpToFileAction;
+    QAction *m_jumpToFileInNextSplitAction;
     QList<QAction *> m_modifyingActions;
 
     uint m_optionalActions;