Update compatibilityMode versions.

Rename constants, l10n, and comments to reflect the actual version that
the new compatibilityMode is deployed in.
Debatable. It's purely a client layer issue, it has no effect on the network; even auto-update will use the old format for the time being. In the past we have taken the view that disruptive client level changes can wait for mandatories... but a mandatory is disruptive ...