DOC: hashing: update link to hashing functions

Bret Mulvey, the author of the article cited in this pulication
has migrated his work to papa.bretmulvey.com. I was able to
view an archival version of Bret M.'s original post
(http://home.comcast.net/~bretm/hash/3.html) and have validated
that this is the same paper that is originally cited.

(cherry picked from commit bbf697e7520df4031ac4650f43b95e926d29e509)
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit 6223051c42e305b719271833825536d65134b0eb)
Signed-off-by: Willy Tarreau <w@1wt.eu>
1 file changed