Capture and discard MCCPv1 sequences

A client using libtelnet that receives an MCCPv1 subnegotiation from the server will enter a corrupt state, because MCCPv1's protocol actually specifies an invalid subnegotiation sequence.

A better fix would be to capture MCCPv1 as per here but then enable compression as if it were MCCPv2. Open for discussion (or not)!