This patch adds initial eventlog support on win32. It's good enough for
most purposes, but we will probably want a specific message DLL later to
format the messages nicer.
The patch mimcs the syslog handling in most cases. It also hijacks the
syslog guc variable. Since syslog is not available on win32, it's
meaning is redefined as eventlog. So syslog=1 means eventlog+stdout,
syslog=2 means just eventlog.
For reviews and application to head if nobody objects.
//Magnus
<<eventlog.patch>>