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/webkit/webkit.status b/test/webkit/webkit.status
index 971cf46..fa52742 100644
--- a/test/webkit/webkit.status
+++ b/test/webkit/webkit.status
@@ -35,9 +35,8 @@
   'dfg-inline-arguments-reset-changetype': [PASS, FAIL],
   # TODO(turbofan): We run out of stack earlier on 64-bit for now.
   'fast/js/deep-recursion-test': [PASS, NO_VARIANTS],
-  # This test leads to a SyntaxError from conflicting let declarations
-  # in ES2015
-  'function-declarations-in-switch-statement': [FAIL],
+  # Irregexp interpreter overflows stack. We should just not crash.
+  'fast/js/regexp-stack-overflow': [PASS, FAIL],
 }],  # ALWAYS
 ['mode == debug', {
   # Too slow in debug mode.