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/test/mjsunit/debug-script.js b/test/mjsunit/debug-script.js
index 8874960..5396415 100644
--- a/test/mjsunit/debug-script.js
+++ b/test/mjsunit/debug-script.js
@@ -73,8 +73,8 @@
 
 // This has to be updated if the number of native scripts change.
 assertEquals(%NativeScriptsCount(), named_native_count);
-// Only the 'gc' extension is loaded.
-assertEquals(1, extension_count);
+// The 'gc' extension and one or two extras scripts are loaded.
+assertTrue(extension_count == 2 || extension_count == 3);
 // This script and mjsunit.js has been loaded.  If using d8, d8 loads
 // a normal script during startup too.
 assertTrue(normal_count == 2 || normal_count == 3);