Allow a v4 link protocol for 4-byte circuit IDs.

src/or/buffers.c

src/or/channel.h

src/or/channeltls.c

src/or/circuitbuild.c

src/or/circuitlist.c

src/or/command.c

src/or/connection.c

src/or/connection_or.c

src/or/connection_or.h

src/or/cpuworker.c

src/or/or.h

src/or/relay.c

src/or/relay.h

src/or/router.c