Don’t use only last protocol from getaddrinfo

Don’t use only last protocol from getaddrinfo

Problem reported by Ken Brown in:
http://lists.gnu.org/archive/html/emacs-devel/2016-05/msg00483.html
* src/process.c (conv_addrinfo_to_lisp): New function.
(connect_network_socket): Arg is now a list of addrinfos, not
merely IP addresses.  All uses changed.  Use protocol from
each addrinfo.
(Fmake_network_process): Accumulate protocols into addrinfos
rather than just using the last one found.
(check_for_dns): Accumulate protocols here, too.
* src/process.h (struct Lisp_Process): Remove ai_protocol;
no longer needed.