Tor control spec doesn't properly specify reply format

The control spec does not sufficiently specify how to generically parse multi line replies from the controller. The intent seems to be that multi line response data is terminated by a '.' line.

However, this is not specified in the control spec section 2.3 and the reply description there is insufficient to properly recognize multi-line reply packets leading to bugs like: https://trac.torproject.org/projects/tor/ticket/16990