adjusted visibility to permit passing of tests on mingw for serialization library

test/Jamfile

@@ -24,6 +24,5 @@ import ../../config/checks/config : requires ;
 run binary_search_test.cpp ;
 run is_sorted_test.cpp ;
 run numeric_traits_test.cpp ;
-run test_utf8_codecvt.cpp : :
-  : [ requires std_wstreambuf ]
-  ;
+# run test_utf8_codecvt.cpp : : : [ requires std_wstreambuf ] ;
+run test_utf8_codecvt.cpp ;