The new ebuild for postfix 2.0.12 requests the 0.8.13 version of the postfix_tls extension, which is no longer available. Postfix will build and run correctly with the new version (0.8.14) http://www.aet.tu-cottbus.de/personen/jaenicke/pfixtls/
just a version change, I wish they would leave the old versions available when they bump on me. Thanks for the reminder.