Fix an off-by-one issue with framing that RabbitMQ is forgiving about
Fix an off-by-one issue with framing that RabbitMQ is forgiving about

Current RabbitMQ versions are forgiving about clients exceeding max negotiated
frame size but this will change soon.

Reported by Matthias Radestock.

ruby-amqp/amq-protocol,ruby-amqp/amq-protocol