Move OS::MemCopy and OS::MemMove out of platform to utils

src/scanner.h

Index: src/scanner.h
diff --git a/src/scanner.h b/src/scanner.h
index 037da5b1739a302cbdda71ce50e82a3055c0d712..eeed183cdfcf5f2ee8c64d1a813db4c2f697dab9 100644
--- a/src/scanner.h
+++ b/src/scanner.h
@@ -258,7 +258,7 @@ class LiteralBuffer {
 
   void ExpandBuffer() {
     Vector<byte> new_store = Vector<byte>::New(NewCapacity(kInitialCapacity));
-    OS::MemCopy(new_store.start(), backing_store_.start(), position_);
+    MemCopy(new_store.start(), backing_store_.start(), position_);
     backing_store_.Dispose();
     backing_store_ = new_store;
   }