Update tor-spec.txt to reflect proposal 198 ("Restore semantics of TLS ClientHello")

I just merged legacy/trac#4744 (moved) into master, to implement the client side of Proposal 198. We should update tor-spec.txt to match.

changed milestone to %Tor: 0.2.3.x-final in legacy/trac

added component::core tor/tor in Legacy / Trac milestone::Tor: 0.2.3.x-final in Legacy / Trac priority::medium in Legacy / Trac resolution::fixed in Legacy / Trac status::closed in Legacy / Trac tor-client in Legacy / Trac type::task in Legacy / Trac labels

See branch "prop198_merge" in my public torspec repo.

Trac:
Status: new to needs_review

Merged.

Trac:
Status: needs_review to closed
Resolution: N/A to fixed

Trac:
Keywords: N/A deleted, tor-client added

Trac:
Component: Tor Client to Tor

closed

moved from legacy/trac#6144 (moved)

added Task label and removed 1 deleted label

added Client label and removed 1 deleted label