Eqaf - Constant time equal function on string

From some crypto libraries like
digestif or
Callipyge, it needed to have a
constant time equal function to avoid timing attacks. To avoid replication of
code and ensure maintainability of this kind of function, we decide to provide a
little package which implements equal function on string.

This package provides 2 implementations (a C implementation which comes from
OpenBSD's code and an OCaml implementation which is simply a translation of the
C code) well tested to check constant time assumption (see tests).

Happy hacking!