Replace OS::MemCopy with OS::MemMove (just as fast but more flexible).

src/platform.h

Index: src/platform.h
diff --git a/src/platform.h b/src/platform.h
index 1c655da3005c0c0b8ee562d42cced578572be662..a2517d954df21983f8f13c291e44cc6867648354 100644
--- a/src/platform.h
+++ b/src/platform.h
@@ -337,17 +337,27 @@ class OS {
   static void ReleaseStore(volatile AtomicWord* ptr, AtomicWord value);
 
 #if defined(V8_TARGET_ARCH_IA32)
-  // Copy memory area to disjoint memory area.
-  static void MemCopy(void* dest, const void* src, size_t size);
   // Limit below which the extra overhead of the MemCopy function is likely
   // to outweigh the benefits of faster copying.
   static const int kMinComplexMemCopy = 64;
-  typedef void (*MemCopyFunction)(void* dest, const void* src, size_t size);
 
+  // Copy memory area. No restrictions.
+  static void MemMove(void* dest, const void* src, size_t size);
+  typedef void (*MemMoveFunction)(void* dest, const void* src, size_t size);
+
+  // Keep the distinction of "move" vs. "copy" for the benefit of other
+  // architectures.
+  static void MemCopy(void* dest, const void* src, size_t size) {
+    MemMove(dest, src, size);
+  }
 #else  // V8_TARGET_ARCH_IA32
+  // Copy memory area to disjoint memory area.
   static void MemCopy(void* dest, const void* src, size_t size) {
     memcpy(dest, src, size);
   }
+  static void MemMove(void* dest, const void* src, size_t size) {
+    memmove(dest, src, size);
+  }
   static const int kMinComplexMemCopy = 16 * kPointerSize;
 #endif  // V8_TARGET_ARCH_IA32