wanted: hash stress tests

[Leopold Toetsch]

I'm currently rewriting the hash implementation in src/hash.c. The new 
hash structure has just one piece of malloced memory with bucket 
pointers and buckets in one piece.

But before comitting I'd like to have some stress and benchmarks tests 
that first show that my implementation is correct and of course that 
it's faster too ;-)

I'll ci what I have so far as src/new_hash.c first, when it's usable.
Thanks,
leo