Update V8 to r5388 as required by WebKit r66666

Change-Id: Ib3c42e9b7226d22c65c7077c543fe31afe62a318
diff --git a/src/memory.h b/src/memory.h
index 503492a..27f32f7 100644
--- a/src/memory.h
+++ b/src/memory.h
@@ -36,6 +36,10 @@
 
 class Memory {
  public:
+  static uint8_t& uint8_at(Address addr) {
+    return *reinterpret_cast<uint8_t*>(addr);
+  }
+
   static uint16_t& uint16_at(Address addr)  {
     return *reinterpret_cast<uint16_t*>(addr);
   }