Help: Create separate help widget class

That contains the tool bar together with a help viewer,
which can also be used for an external help window, and later be
extended to also replace the extra "central widget".

Change-Id: I73fac4c135b985cbe47062b90783f156b5062005
Reviewed-by: Karsten Heimrich <karsten.heimrich@digia.com>

src/plugins/help/textbrowserhelpviewer.h

@@ -52,10 +52,6 @@ public:
     QFont viewerFont() const;
     void setViewerFont(const QFont &font);
 
-    void scaleUp();
-    void scaleDown();
-
-    void resetScale();
     qreal scale() const;
 
     QString title() const;
@@ -77,6 +73,9 @@ public:
                   bool incremental, bool fromSearch, bool *wrapped = 0);
 
 public slots:
+    void scaleUp();
+    void scaleDown();
+    void resetScale();
     void copy();
     void stop();
     void forward();