don't use annoying and unneeded in C++ casts of NULL to "T *" in all other files neither

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58227 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/cursor.cpp

@@ -106,7 +106,7 @@ public:
     virtual void OnExit()
     {
         delete gs_globalCursor;
-        gs_globalCursor = (wxCursor *)NULL;
+        gs_globalCursor = NULL;
     }
 };