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 <[email protected]>
Acked-by: Jan Beulich <[email protected]>

Author: dozylynx

xen/include/public/errno.h

@@ -102,13 +102,15 @@ XEN_ERRNO(EILSEQ,	84)	/* Illegal byte sequence */
 XEN_ERRNO(ERESTART,	85)	/* Interrupted system call should be restarted */
 #endif
 XEN_ERRNO(ENOTSOCK,	88)	/* Socket operation on non-socket */
+XEN_ERRNO(EMSGSIZE,	90)	/* Message too large. */
 XEN_ERRNO(EOPNOTSUPP,	95)	/* Operation not supported on transport endpoint */
 XEN_ERRNO(EADDRINUSE,	98)	/* Address already in use */
 XEN_ERRNO(EADDRNOTAVAIL, 99)	/* Cannot assign requested address */
 XEN_ERRNO(ENOBUFS,	105)	/* No buffer space available */
 XEN_ERRNO(EISCONN,	106)	/* Transport endpoint is already connected */
 XEN_ERRNO(ENOTCONN,	107)	/* Transport endpoint is not connected */
 XEN_ERRNO(ETIMEDOUT,	110)	/* Connection timed out */
+XEN_ERRNO(ECONNREFUSED,	111)	/* Connection refused */
 
 #undef XEN_ERRNO
 #endif /* XEN_ERRNO */