Added configure test for const_cast<>(), and enabled it

for MSVC 5 and 6, and MinGW; use const_cast<>() in
wxConstCast if it is available.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@19537 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/object.h

@@ -305,7 +305,11 @@ name##PluginSentinel  m_pluginsentinel;
 #define wxDynamicCastThis(className) \
  (IsKindOf(&className::sm_class##className) ? (className *)(this) : (className *)0)
 
+#ifdef HAVE_CONST_CAST
+#define wxConstCast(obj, className) const_cast<className *>(obj)
+#else
 #define wxConstCast(obj, className) ((className *)(obj))
+#endif
 
 
 #ifdef __WXDEBUG__