Revert the reversion of the elegant fix of wrong MSVC compiler warning

This reverts commit 57c68d144e.

src/TrackPanelDrawingContext.h

@@ -19,19 +19,13 @@ class wxDC;
 
 #include <wx/mousestate.h>
 
-// MSVC 2013 says this can't be instantiated - but in fact it can
-// using {} syntax.
-// As it's a bogus warning caused by a bug in MSVC2013, it's Ok to disable it.
-#pragma warning( push )
-#pragma warning( disable : 4510)
-#pragma warning( disable : 4610)
-
 struct TrackPanelDrawingContext {
    wxDC &dc;
    UIHandlePtr target;
    wxMouseState lastState;
+
+   // This redundancy fixes an MSVC compiler warning:
+   TrackPanelDrawingContext() = delete;
 };
 
-#pragma warning( pop ) 
-
 #endif