2.13.1

Fix only.

• "Check again" on the Updates screen now really re-checks. Release lookups are cached for six hours, and WordPress's force-check clears its own update transient but knows nothing about that cache, so a release published in the last six hours stayed invisible however many times the button was pressed -- which reads as the updater being broken rather than being cached. A forced check now bypasses the cache; ordinary checks still use it.