Fix wxListCtrl sort callback signature in the test under Win64.

Use wxIntPtr instead of long which is not big enough to hold a pointer in
Win64 builds.

Closes #4309.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@76994 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

tests/controls/listbasetest.cpp

@@ -445,7 +445,7 @@ namespace
 {
     //From the sample but fixed so it actually inverts
     int wxCALLBACK
-    MyCompareFunction(long item1, long item2, wxIntPtr WXUNUSED(sortData))
+    MyCompareFunction(wxIntPtr item1, wxIntPtr item2, wxIntPtr WXUNUSED(sortData))
     {
         // inverse the order
         if (item1 < item2)