warnings--

If we passed not-a-ketama-object, the 'find-magic' bit would fail and
we would use our ketama pointer without initializing it.
warnings--

param was unused in both cases.
Hashing constructs should use the length

This fix adds a length field to all the hash operations to allow ketama
to shard on keys that contain binary data.  Previously, it was expecting
null-terminated strings which fails if your keys happen to contain a
0-byte.