Add "unicode_strings" test case for new Python 3 behavior

Examples/test-suite/unicode_strings.i

@@ -0,0 +1,15 @@
+%module unicode_strings
+
+%include <std_string.i>
+
+%inline %{
+
+const char* test_c_str(void) {
+        return "h\xe9llo";
+}
+
+std::string test_std_string(void) {
+        return std::string("h\xe9llo");
+}
+
+%}