Subzero: Fix build problem against LLVM trunk.

pnacl-llvm/MemoryObject.cpp

+//===- MemoryObject.cpp - Abstract memory interface -----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/MemoryObject.h"
+using namespace llvm;
+  
+MemoryObject::~MemoryObject() {
+}