CA-94829: Bindings to the TCP keepalive settings

Signed-off-by: Jon Ludlam <jonathan.ludlam@eu.citrix.com>
Merge pull request #128 from jonludlam/CA-94829-clearwater

CA-94829: Bindings to the TCP keepalive settings
Use unbuffered I/O to read from /dev/(u)random

Signed-off-by: Vincent Bernardoff <vincent.bernardoff@ocamlpro.com>