Avoid allocation on interop for system/generic categories; fix DLL interoperability on msvc-14.x by poking into std::system_category::_Addr

test/std_single_instance_2.cpp

@@ -31,4 +31,10 @@ EXPORT std::error_code get_generic_code()
 
 } // namespace lib2
 
+#else
+
+EXPORT void lib2_f()
+{
+}
+
 #endif