Deprecate second parameter of wxSlider::SetTickFreq().

This parameter was never needed nor properly documented. Simply remove it from
SetTickFreq() and keep the overload still taking it for backwards
compatibility only.

Closes #12907.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66844 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/univ/slider.h

@@ -77,7 +77,6 @@ public:
     virtual void SetThumbLength(int lenPixels);
     virtual int GetThumbLength() const;
 
-    virtual void SetTickFreq(int n, int WXUNUSED(dummy) = 0);
     virtual int GetTickFreq() const { return m_tickFreq; }
 
     // wxUniv-specific methods
@@ -137,6 +136,9 @@ protected:
         INVALID_THUMB_VALUE = -0xffff
     };
 
+    // Platform-specific implementation of SetTickFreq
+    virtual void DoSetTickFreq(int freq);
+
     // overridden base class virtuals
     virtual wxSize DoGetBestClientSize() const;
     virtual void DoDraw(wxControlRenderer *renderer);