merge upstream Move linear search to binary search

 eric@titan:~/src/libchash$ git show 448f47f
 commit 448f47fc232382c2ea5bb379eeadfd34fd6b5d28
 Author: Damian Gryski <damian@gryski.com>
 Date:   Mon Dec 16 10:09:48 2013 +0100

     Move linear search to binary search.

     For the 100000 searches done during the unit test, this drops the cpu
     cycles from 74M down to 17M.