Updated Eventch doc.
Updated Eventch doc.

euanh/ocaml-xen-lowlevel-libs,djs55/ocaml-xen-lowlevel-libs,djs55/ocaml-xen-lowlevel-libs,djs55/ocaml-xen-lowlevel-libs,euanh/ocaml-xen-lowlevel-libs,euanh/ocaml-xen-lowlevel-libs,djs55/ocaml-xen-lowlevel-libs,jonludlam/ocaml-xen-lowlevel-libs