Move assert.h/assert.cc from runtime/vm to runtime/platform

runtime/vm/os_macos.cc

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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/os.h"
+
 #include <errno.h>
 #include <limits.h>
 #include <mach/mach.h>
 #include <mach/clock.h>
 #include <mach/mach_time.h>
 #include <sys/time.h>
 #include <sys/resource.h>
 #include <unistd.h>
 
 #include "vm/isolate.h"
-#include "vm/os.h"
 #include "vm/utils.h"
 
 namespace dart {
 
 bool OS::BreakDownSecondsSinceEpoch(time_t seconds_since_epoch,
                                     bool in_utc,
                                     BrokenDownDate* result) {
   struct tm tm_result;
   struct tm* error_code;
   if (in_utc) {
@@ skipping 166 matching lines @@
 void OS::Abort() {
   abort();
 }
 
 
 void OS::Exit(int code) {
   exit(code);
 }
 
 }  // namespace dart