wp_cache user cache uses user_login AND user_id as keys

[donncha]

The wp_cache user group uses both user_login and user_id as keys. This has the side-effect that existing numeric logins get confused between their username and the data of a user with the same user_id.

Fix: add a "userlogins" group and change all references to the "users" cache group using user_login as a key so they use the "userlogins" group.

Possibly affected files: wp-admin/admin-db.php wp-includes/cache.php wp-includes/capabilities.php wp-includes/functions.php wp-includes/pluggable-functions.php wp-includes/registration-functions.php
I'll try to dig up a patch for this shortly.

[ryan]

(In [3330]) Cache user ids and user logins separately to avoid collision. Props donncha. fixes #2096