pgsql: Work around reported problem that AIX's getaddrinfo() doesn't

Log Message:
-----------
Work around reported problem that AIX's getaddrinfo() doesn't seem to zero
sin_port in the returned IP address struct when servname is NULL. This has
been observed to cause failure to bind the stats collection socket, and
could perhaps cause other issues too. Per reports from Brad Nicholson
and Chris Browne.

Modified Files:
--------------
pgsql/src/backend/libpq:
ip.c (r1.36 -> r1.37)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/libpq/ip.c.diff?r1=1.36&r2=1.37)