Update postfix package to 2.8.3.

* pkgsrc change: remoe mysql4 from PKG_OPTIONS.

Securiy release for Memory corruption in Postfix SMTP server Cyrus SASL
support: http://www.postfix.org/CVE-2011-1720.html

20110411

Cleanup: postscreen(8) and verify(8) daemons now lock their
respective cache file exclusively upon open, to avoid massive
cache corruption by unsupported sharing. Files: util/dict.h,
util/dict_open.c, verify/verify.c, postscreen/postscreen.c.

20110414

Bugfix (introduced with Postfix SASL patch 20000314): don't
reuse a server SASL handle after authentication failure.
Problem reported by Thomas Jarosch of Intra2net AG. File:
smtpd/smtpd_proto.c.

(taca)