pgsql: Tweak pgbench.c to remove the hidden assumption that a WIN32

Log Message:
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Tweak pgbench.c to remove the hidden assumption that a WIN32 machine
couldn't possibly HAVE_GETOPT. I believe this is the most appropriate
form of the patch submitted 2007-08-07 by Hiroshi Saito, though not
having a Windows build environment I won't know for sure till I see
the buildfarm results.

Modified Files:
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pgsql/contrib/pgbench:
pgbench.c (r1.71 -> r1.72)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pgbench/pgbench.c?r1=1.71&r2=1.72)