Work around systems returning obsolete EAI_NODATA.

Work around systems returning obsolete EAI_NODATA.

Older systems that provide the older RFC-2553 implementation of
getaddrinfo, rather than the current RFC-3493, and systems that do not
provide this getaddrinfo() interface at all and thus use the replacement
functions from libesmtp/getaddrinfo.?, might return EAI_NODATA when a
host is registered in DNS as MX or similar, but without A or AAAA
records.  Handle this situation when checking for multidrop aliases and
treat EAI_NODATA the same as EAI_NONAME, i. e. name cannot be resolved.

The proper fix, however, is to upgrade the operating system.