Work around wxNumValidator compilation problems with MSVC 6.

Surprisingly, MSVC 6 seems to be able to compile most of the code but chokes
on a wxCOMPILE_TIME_ASSERT involving an inherited typedef. As this assert is
not critical, simply disable it for this compiler.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66722 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/valnum.h

@@ -135,11 +135,17 @@ public:
 
     typedef typename BaseValidator::LongestValueType LongestValueType;
 
+    // FIXME-VC6: This compiler fails to compile the assert below with a
+    // nonsensical error C2248: "'LongestValueType' : cannot access protected
+    // typedef declared in class 'wxIntegerValidatorBase'" so just disable the
+    // check for it.
+#ifndef __VISUALC6__
     wxCOMPILE_TIME_ASSERT
     (
         sizeof(ValueType) <= sizeof(LongestValueType),
         UnsupportedType
     );
+#endif // __VISUALC6__
 
     void SetMin(ValueType min)
     {