Avoid duplicate DNS requests if answer is longer than a implementation

Avoid duplicate DNS requests if answer is longer than a implementation
limit

        [BZ #14307]
        * sysdeps/posix/getaddrinfo.c (gaih_inet): Increase the size of
        the temporary buffer used to invoke __gethostbyname2_r,
        __gethostbyaddr_r and gethostbyname4_r to make room for struct
        host_data / struct gaih_addrtuple.
        * resolv/nss_dns/dns-host.c (global scope): Move definition of
        implementation constants MAX_NR_ALIASES and MAX_NR_ADDRS to
        header file nss/nsswitch.h.
        * nss/nsswitch.h (global scope): Add definition of implementation
        constants MAX_NR_ALIASES and MAX_NR_ADDRS (moved from
        resolv/nss_dns/dns-host.c).