To be done after 1.11-stable is branched.

Scan the codebase for deprecations marked with a 1.12 deadline and remove them (ack deprecation.*1.12). All deprecations with a 1.12 deadline have been shipped (at least) in 1.10 and 1.11.

Marked for a 1.11.0 release so it's done at the time of 1.11-stable branching, but please move to 1.12.0 when done.