Revert "Revert "Upgrade to 5.0.71.48"" DO NOT MERGE

This reverts commit f2e3994fa5148cc3d9946666f0b0596290192b0e,
and updates the x64 makefile properly so it doesn't break that
build.

FPIIM-449

Change-Id: Ib83e35bfbae6af627451c926a9650ec57c045605
(cherry picked from commit 109988c7ccb6f3fd1a58574fa3dfb88beaef6632)
diff --git a/tools/run-valgrind.gyp b/tools/run-valgrind.gyp
new file mode 100644
index 0000000..d06be93
--- /dev/null
+++ b/tools/run-valgrind.gyp
@@ -0,0 +1,26 @@
+# Copyright 2016 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+{
+  'conditions': [
+    ['test_isolation_mode != "noop"', {
+      'targets': [
+        {
+          'target_name': 'run_valgrind_run',
+          'type': 'none',
+          'dependencies': [
+            '../src/d8.gyp:d8_run',
+          ],
+          'includes': [
+            '../build/features.gypi',
+            '../build/isolate.gypi',
+          ],
+          'sources': [
+            'run-valgrind.isolate',
+          ],
+        },
+      ],
+    }],
+  ],
+}