Hash functions and CountHashTab

[lekcyjna123]

Hi, Here is a pull request which adds hash tables. In particularly:

• Added implementation of two non-cryptographic hashes: -- Lookup3 (http://www.burtleburtle.net/bob/hash/doobs.html) -- SipHash (https://eprint.iacr.org/2012/351.pdf)
• Added CountHashTab

I am not sure how to test them, so comments are welcome.

Hash functions I test using statistical test to check if they hash into uniform distribution, but sadly for small input data (from range [0,1023]) there is some bias and statistical tests fails... Whats more I am not sure if we want to have tests based on statistics, because this can cause instability.

[tilk]

Whats more I am not sure if we want to have tests based on statistics, because this can cause instability.

We're not supposed to implement some dreamed up hash functions, but some existing ones with established properties. The only thing to test is to compare a hardware implementation to a software one.