queues for TIOCSETA[W]. Swapping an even number of times broke
the queue resource limits. This would have broken CRTSCTS flow
control if the clist slush list was used up.
Don'concatenate the queues for TIOCSETA[W] if one of the queues
has a resource limit of 0. Concatenation would cause a panic if
one of the queues is nonempty and the other is limited to length
0. This may have caused panics in PPPDISC.
Wake up readers after all transitions of ICANON. When ICANON is
turned off it is quite likely that characters will become available
to be read.
Reduce indentation near these changes.
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