Update V8 to r6101 as required by WebKit r74534

Change-Id: I7f84af8dd732f11898fd644b2c2b1538914cb78d
diff --git a/src/d8.h b/src/d8.h
index 30f04c7..de1fe0d 100644
--- a/src/d8.h
+++ b/src/d8.h
@@ -138,6 +138,10 @@
   static Handle<Value> DebugCommandToJSONRequest(Handle<String> command);
 #endif
 
+#ifdef WIN32
+#undef Yield
+#endif
+
   static Handle<Value> Print(const Arguments& args);
   static Handle<Value> Write(const Arguments& args);
   static Handle<Value> Yield(const Arguments& args);