OrderedHashTable is an insertion-ordered HashTable based on
Jason Orendorff's writeup of a data structure attributed to Tyler Close:
https://wiki.mozilla.org/User:Jorend/Deterministic_hash_tables

It is intended as the new backing store for JSSet/JSMap, as ES6 requires
insertion-order-based iteration. Note, however, that in the interest of
keeping the initial check-in small this patch does not yet include any
iteration support.

This change also doesn't yet touch any existing behavior, but in
a branch I've verified that these structures pass the existing
JSSet/JSMap mjsunit tests.

BUG=v8:1793
LOG=N
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/220293002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20522 ce2b1a6d-e550-0410-aec6-3dcde31c8c00