pgsql-server: Tweaks per discussion with Magnus: suppress chatter on

Log Message:
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Tweaks per discussion with Magnus: suppress chatter on unpatched MinGW
systems, add verbose logging (at DEBUG4) to help identify why a given
time zone is not matched.

Modified Files:
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pgsql-server/src/timezone:
pgtz.c (r1.15 -> r1.16)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/timezone/pgtz.c.diff?r1=1.15&r2=1.16)