MEDIUM: mux-quic: handle when sending buffer is full

Handle the case when the app layer sending buffer is full. A new flag
QC_SF_BLK_MROOM is set in this case and the transfer is interrupted. It
is expected that then the conn-stream layer will subscribe to SEND.

The MROOM flag is reset each time the muxer transfer data from the app
layer to its own buffer. If the app layer has been subscribed on SEND it
is woken up.
4 files changed