Revert "merged branch javer/hhvm-array-traversable (PR #1192)"

This reverts commit 0d97eb95288c6f08d5c46e9aa5706f2341a34e29, reversing
changes made to 4fcaf0c5fc91435cf625c20c0ecbd29c4f8b25a1.

This change is not needed anymore as HHVM has been fixed as of 2.3.0.