Output snappiness improvements.

When the system checks for an incoming byte, if there's any pending
output, send it immediately, bypassing the outbuf highwater mark.

This allows the final non-full packet to be sent without waiting
for the OutbufDrainTimeout (default 10ms), and makes a big difference
when doing a large number of ANSI queries (send an ANSI code, wait
for a response).  There's a small but noticable placebo effect as
well that makes everything feel smoother.

This commit also cleans up the output thread where it pulls from
the ring buffer into the linear buffer to take advantage of the new
event-based ring buffers.  Much easier to read now.

Speaking of easier to read, this also includes some whitespace
fixups.