Implement large/split create cells (proposal 249)

In order to support postquantum crypto for relay encryption, we need to let create cells become bigger.

I wrote a proposal for that (prop249) but it needs more work. We should do the server-side in 028 if we hope to get it deployed in 029.

changed milestone to %Tor: unspecified

added component::core tor/tor milestone::Tor: unspecified points::medium/large priority::high prop249 protocol severity::normal status::new tor-client tor-relay type::defect labels

It is impossible that we will fix all 226 currently open 028 tickets before 028 releases. Time to move some out. This is my second pass through the "new" and tickets, looking for things to move to 0.2.9.

Trac:
Milestone: Tor: 0.2.8.x-final to Tor: 0.2.9.x-final

tickets market to be removed from milestone 029

Trac:
Milestone: Tor: 0.2.9.x-final to Tor: 0.2.???

Milestone renamed

Trac:
Milestone: Tor: 0.2.??? to Tor: 0.3.???

Finally admitting that 0.3.??? was a euphemism for Tor: unspecified all along.

Trac:
Milestone: Tor: 0.3.??? to Tor: unspecified
Keywords: prop249 028-triage deleted, prop249, 028-triage, tor-03-unspecified-201612 added

Remove an old triaging keyword.

Trac:
Keywords: tor-03-unspecified-201612 deleted, N/A added

Trac:
Keywords: 028-triage deleted, N/A added

Trac:
Severity: N/A to Normal
Reviewer: N/A to N/A
Keywords: prop249 deleted, prop249 tor-client tor-relay protocol added

mentioned in issue #17286 (moved)

moved to tpo/core/tor#17279 (closed)

mentioned in issue tpo/core/tor#17286 (closed)