Updated with all of the suggestions thusfar.

==== 
Title: MySQL 5.1 unmasking and upgrade procedures
Author: Robin H. Johnson <robbat2@gentoo.org>
Content-Type: text/plain
Posted: 2010-02-15
Revision: 2
News-Item-Format: 1.0
Display-If-Installed: <dev-db/mysql-5.1

The 5.1 series of MySQL is going to be unmasked at the same time as the release
of this news item. When upgrading from an older major version (including
5.0), you will be required to rebuild everything linked to the
libmysqlclient.so.15.

You can do this by installing app-portage/gentoolkit and running:
# revdep-rebuild --library libmysqlclient.so.15

If you use the Portage 2.2 series, you may also use:
# emerge @preserved-rebuild

The official upgrade docs are available here:
http://dev.mysql.com/doc/refman/5.1/en/upgrade.html

==== 

-- 
Robin Hugh Johnson
Gentoo Linux: Developer, Trustee & Infrastructure Lead
E-Mail     : robbat2@gentoo.org
GnuPG FP   : 11AC BA4F 4778 E3F6 E4ED  F38E B27B 944E 3488 4E85