Adding a bitset module in standard for binary operations
Adding perfect_hashing module (with perfect numbering)
Merge: Bitset and perfect_hashing

Adding a bitset module in standard library for binary operations required for perfect hashing.

And a perfect_hashing module with perfect numbering.

Pull-Request: #440
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>