pgsql: prevent multiplexing Windows kernel event objects we listen for

Log Message:
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prevent multiplexing Windows kernel event objects we listen for across various sockets - should fix the occasional stats test regression failures we see.

Tags:
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REL8_0_STABLE

Modified Files:
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pgsql/src/backend/port/win32:
socket.c (r1.8 -> r1.8.4.1)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/port/win32/socket.c.diff?r1=1.8&r2=1.8.4.1)