Implement date library functions in C++.

src/assembler.h

Index: src/assembler.h
diff --git a/src/assembler.h b/src/assembler.h
index e7c92b451c09df9feeaa74471cab8dbc5b0bd157..5063879ae4c4a19f7046471e8a64bceb981d29d0 100644
--- a/src/assembler.h
+++ b/src/assembler.h
@@ -595,6 +595,9 @@ class ExternalReference BASE_EMBEDDED {
   static ExternalReference transcendental_cache_array_address(Isolate* isolate);
   static ExternalReference delete_handle_scope_extensions(Isolate* isolate);
 
+  static ExternalReference get_date_field_function(Isolate* isolate);
+  static ExternalReference date_cache_stamp(Isolate* isolate);
+
   // Deoptimization support.
   static ExternalReference new_deoptimizer_function(Isolate* isolate);
   static ExternalReference compute_output_frames_function(Isolate* isolate);