correct typo in comment
This was introduced in http://hg.rabbitmq.com/rabbitmq-server/rev/4852382b462b
small refactor: simplify AMQP version negotiation a little bit
simplify
merge stable into bug25939
further optimise frame reading

Handle complete frames in one go, if possible, rather than header and
payload separately. This essentially halves the amount of binary
splitting in the framing code.

Note that we only do this when the buffer contains just one
binary. Tests have shown that attempting to introduce this
optimisation when the buffer comprises multiple binaries hurts
performance for large messages. That's presumably because we end up
constructing larger intermediate binaries.