If maxline is too small, messages won't get through.  If maxline is too large *huge* messages will get through...and the DDOS danger of exhausting the server's resources will occur.  So, we really ought to provide a way to limit the maximum message size *anyway*...at which point a separate maxline value doesn't make any sense, since the RFC specifies no maximum line size.

I'm much more comfortable setting a large maximum message size than setting a large enough maximum line size to permit that size of message consisting of mostly a single line.  Since we aren't going to back out the DDOS fix, we have to put the limit *somewhere*.  At least in 3.6 we can make it easy for the application to set it.  (Programs using earlier versions will just have to monkey-patch, unfortunately...which they have to do right now anyway.)