Make wxWindow::HasScrollbar() respect wxScrolled::ShowScrollbars().

Override CanScroll() in wxScrolled to return the real state of the scrollbar
instead of just relying on the wx[HV]SCROLL styles.

Closes #15440.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74714 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk1/scrolwin.h

@@ -25,6 +25,7 @@ public:
                                int noUnitsX, int noUnitsY,
                                int xPos = 0, int yPos = 0,
                                bool noRefresh = false);
+    virtual bool IsScrollbarShown(int orient) const;
     virtual void AdjustScrollbars();
 
 protected: