Revert "Revert "Upgrade to 5.0.71.48""

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

Change-Id: Ib83e35bfbae6af627451c926a9650ec57c045605
diff --git a/test/mjsunit/array-concat.js b/test/mjsunit/array-concat.js
index 97bd85a..6e25b5c 100644
--- a/test/mjsunit/array-concat.js
+++ b/test/mjsunit/array-concat.js
@@ -29,6 +29,19 @@
  * @fileoverview Test concat on small and large arrays
  */
 
+
+(function testStringWrapperConcat() {
+  var concat = Array.prototype.concat;
+  var str = new String('abcd');
+  assertEquals([1,2,3,new String('abcd')], [1, 2, 3].concat(str));
+  assertEquals([new String("abcd")], concat.call(str));
+
+  var array = [1, 2, 3];
+  array.__proto__ = str;
+  array.length = 4;
+  assertEquals([1,2,3,'d'], concat.call(array));
+})()
+
 var poses;
 
 poses = [140, 4000000000];