COMP: Make sure gcc 2.96 sstream header is not used.

kwsysPlatformTestsCXX.cxx

@@ -46,6 +46,9 @@ int main() { return 0; }
 
 #ifdef TEST_KWSYS_IOS_USE_SSTREAM
 #include <sstream>
+#if defined(__GNUC__) && __GNUC__ == 2 && __GNUC_MINOR__ == 96
+# error "GCC 2.96 stringstream is buggy"
+#endif
 int main()
 { 
   std::ostringstream ostr;