Move upgrader_process_complete for core to its proper place in Core_Upgrader.

This means it will be firing as a JS redirect is taking place if the update is from pre-3.4. Acceptable.

props dd32.
fixes #25659.


git-svn-id: http://develop.svn.wordpress.org/trunk@25861 602fd350-edb4-49c9-b593-d223f7449a82
Improve inline documentation for the `wp_get_sites()` return value.

Fixes #25645.


git-svn-id: http://develop.svn.wordpress.org/trunk@25862 602fd350-edb4-49c9-b593-d223f7449a82
Updates: Saner stats and rollback handling. WP.org now collects basic stats on non-auto updates as they have been hugely informative.

props dd32 for initial patch.
fixes #25657.


git-svn-id: http://develop.svn.wordpress.org/trunk@25863 602fd350-edb4-49c9-b593-d223f7449a82