Add initial hydrogenized NewStringAddStub.

test/mjsunit/new-string-add.js

Index: test/mjsunit/new-string-add.js
diff --git a/test/mjsunit/string-add.js b/test/mjsunit/new-string-add.js
similarity index 98%
copy from test/mjsunit/string-add.js
copy to test/mjsunit/new-string-add.js
index f226ca18c491ad47c2e176274d420804f1f9be7a..f5b7cbfbf2d94c4bac9a06f285da9de1455df203 100644
--- a/test/mjsunit/string-add.js
+++ b/test/mjsunit/new-string-add.js
@@ -1,4 +1,4 @@
-// Copyright 2009 the V8 project authors. All rights reserved.
+// Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -25,6 +25,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+// Flags: --new-string-add
+
 assertEquals("ab", "a" + "b", "ll");
 
 assertEquals("12", "1" + "2", "dd");