Editor: Add actions for view page/line up/down.

Task-number: QTCREATORBUG-4994
Change-Id: Ia6ce1a01cd78dd1987404d77f6b0c0da41b4929e
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/texteditor/basetexteditor.h

@@ -290,6 +290,11 @@ public slots:
     void moveLineUp();
     void moveLineDown();
 
+    void viewPageUp();
+    void viewPageDown();
+    void viewLineUp();
+    void viewLineDown();
+
     void copyLineUp();
     void copyLineDown();