[regexp] Add support for dotAll flag

src/assembler.h

Index: src/assembler.h
diff --git a/src/assembler.h b/src/assembler.h
index 2afc6830681a17abb6015ec66a309b67d6179095..d86ba82781fc51baeac854e63ad3b2781fb276a8 100644
--- a/src/assembler.h
+++ b/src/assembler.h
@@ -923,6 +923,9 @@ class ExternalReference BASE_EMBEDDED {
   // Static variable RegExpStack::limit_address()
   static ExternalReference address_of_regexp_stack_limit(Isolate* isolate);
 
+  // Direct access to FLAG_harmony_regexp_dotall.
+  static ExternalReference address_of_regexp_dotall_flag(Isolate* isolate);
+
   // Static variables for RegExp.
   static ExternalReference address_of_static_offsets_vector(Isolate* isolate);
   static ExternalReference address_of_regexp_stack_memory_address(