Implement proposal 221: Stop sending CREATE_FAST

This makes FastFirstHopPK an AUTOBOOL; makes the default "auto"; and
makes the behavior of "auto" be "look at the consensus."
circuit_build_failed: distinguish "got DESTROY" case

Roger spotted this on tor-dev in his comments on proposal 221.

We etect DESTROY vs everything else, since arma likes network
timeout indicating failure but not overload indicating failure.
Merge branch 'prop221_squashed_024'

Conflicts:
	src/or/or.h