Qmux development

[huitema]

QMUX support will be developed in stages:

• do a basic QMUX send test, to show that we can format an outgoing packet,
• do a basic QMUX receive test, to show that we can process an incoming packet,
• formatting of transport parameter frame
• processing of transport
• simulate a "back to back" QMUX connection
• simulate a "back to back" QMUX connection using TLS
• simulate the QMUX/TLS connection over network simulation
• add support for TCP in socket loop
• test end to end QMUX connection

There will be at least one PR for each of these stages.