errno: add POSIX error codes EMSGSIZE, ECONNREFUSED to the ABI

errno: add POSIX error codes EMSGSIZE, ECONNREFUSED to the ABI

EMSGSIZE: Argo's sendv operation will return EMSGSIZE when an excess amount
of data, across all iovs, has been supplied, exceeding either the statically
configured maximum size of a transmittable message, or the (variable) size
of the ring registered by the destination domain.

ECONNREFUSED: Argo's register operation will return ECONNREFUSED if a ring
is being registered to communicate with a specific remote domain that does
exist but is not argo-enabled.

These codes are described by POSIX here:
http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/errno.h.html
    EMSGSIZE     : "Message too large"
    ECONNREFUSED : "Connection refused".

The numeric values assigned to each are taken from Linux, as is the case
for the existing error codes.
    EMSGSIZE     : 90
    ECONNREFUSED : 111

Signed-off-by: Christopher Clark <christopher.clark6@baesystems.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Juergen Gross <jgross@suse.com>