Blender Git Loki

GHash: fix/hugely enhance GHash tests.

Also, fix some stupid mistakes in some new murmur hashing helpers,
and rework quality function to simply compute variance in buckets occupation.

Note latest change has some quite funny effects, looks like variance is always
very close to load of the ghash...

As for performances:
* Globally, ghash and murmur have very similar results, both in speed and quality.
* For integers, ghash usually quicker.
* For strings, oddly murmur is much quicker when adding to ghash, but quite slower
when lookingup in the ghash...

Anyway, still much to do in this area!