Land number collision fix for v8 3.6 by Erik Corry

- If V8 snapshots are enabled then the hash is only randomized at build time.

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backport @10366, @10367 and @10402 to 3.6

Add seed to hash of numeric keyed properties.

Minor cleanups of numeric seeded hashing patch.

Split NumberDictionary into a randomly seeded and an unseeded version.
We don't want to randomize the stub cache.

Review URL: http://codereview.chromium.org/9190001/