Move utils.h and utils.cc from runtime/vm to runtime/platform

runtime/vm/virtual_memory_macos.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/virtual_memory.h"
 
 #include <sys/mman.h>
 #include <unistd.h>
 
 #include "platform/assert.h"
-#include "vm/utils.h"
+#include "platform/utils.h"
 
 namespace dart {
 
 // standard MAP_FAILED causes "error: use of old-style cast" as it
 // defines MAP_FAILED as ((void *) -1)
 #undef MAP_FAILED
 #define MAP_FAILED reinterpret_cast<void*>(-1)
 
 uword VirtualMemory::page_size_ = 0;
 
@@ skipping 44 matching lines @@
   void* address = mmap(reinterpret_cast<void*>(addr), size, prot,
                        MAP_PRIVATE | MAP_ANON | MAP_FIXED,
                        -1, 0);
   if (address == MAP_FAILED) {
     return false;
   }
   return true;
 }
 
 }  // namespace dart