[regexp] Add support for dotAll flag

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 91dc3d04e1da2baea5805d43b3c9520ee1f041ac..2d7d363b5be71190fac9ca18d18a99eb3dad2f45 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -8305,6 +8305,7 @@ class JSRegExp: public JSObject {
     kMultiline = 1 << 2,
     kSticky = 1 << 3,
     kUnicode = 1 << 4,
+    kDotAll = 1 << 5,
   };
   typedef base::Flags<Flag> Flags;