Add wxOSX_USE_COCOA around Cocoa-only OSXApplyAttr() method.

This method is used in wxOSX/Cocoa only.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62607 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/dvrenderers.h

@@ -30,7 +30,9 @@ public:
 
     virtual bool MacRender();
 
+#if wxOSX_USE_COCOA
     virtual void OSXApplyAttr(const wxDataViewItemAttr& attr);
+#endif // Cocoa
 
     virtual wxDC* GetDC(); // creates a device context and keeps it
     void SetDC(wxDC* newDCPtr); // this method takes ownership of the pointer