Update V8 to r6101 as required by WebKit r74534

Change-Id: I7f84af8dd732f11898fd644b2c2b1538914cb78d
diff --git a/src/variables.h b/src/variables.h
index ec76fee..9e460f7 100644
--- a/src/variables.h
+++ b/src/variables.h
@@ -146,6 +146,8 @@
   }
 
   bool IsStackAllocated() const;
+  bool IsParameter() const;  // Includes 'this'.
+  bool IsStackLocal() const;
 
   bool is_dynamic() const {
     return (mode_ == DYNAMIC ||