pgsql: Add code to use Windows getaddrinfo and friends if they exist.

Log Message:
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Add code to use Windows getaddrinfo and friends if they exist. This
has to be tested dynamically if we want to make portable executables.
Chuck McDevitt and Andrew Dunstan.

Modified Files:
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pgsql/src/port:
getaddrinfo.c (r1.17 -> r1.18)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/port/getaddrinfo.c.diff?r1=1.17&r2=1.18)