Support rxvt-style keys again, but this time: support all the variations, put
them in as raw escape sequences rather than fiddling with the values from
terminfo, put them /after/ the terminfo values so the latter take precedence.
Switch the tty key tree over to an (unbalanced) ternary tree which allows
partial matches to be done (they wait for further data or a timer to expire,
like a naked escape).
Mouse and xterm-style keys still expect to be atomic.
Switch tty key input over to happen on a read event. This is a bit more
complicated because of escape input, but in that case instead of processing a
key immediately, schedule a timer and reprocess the bufer when it expires.
This currently assumes that keys will be atomic (ie that if eg F1 is pressed
the entire sequence is present in the buffer). This is usually but not always
true, a change in the tree format so it can differentiate potential (partial)
key sequences will happens soon and will allow this to be fixed.
Not all terminals swap CSI and SS3 on ctrl, so remove that.
Also mark the rxvt special-cases as such until terminfo is updated to have
kLFT5, kRIT5 etc.
Rewrite xterm-keys code (both input and output) so that works (doesn't always
output the same modifiers, accepts all the possible input keys) and is more
understandable.
Support the (mostly new) function key+modifier caps (kIC-kIC7). Most of these
will be caught (soon) by the xterm keys code in xterm itself but some other
descriptions such as rxvt define them as well.
Clean up by introducing a wrapper struct for mouse clicks rather than passing
three u_chars around.
As a side-effect this fixes incorrectly rejecting high cursor positions
(because it was comparing them as signed char), reported by Tom Doherty.
Detect backspace by looking at termios VERASE and translate it into \177
(which matches screen's behaviour if not its termcap/terminfo entry). The
terminfo kbs cap is often wrong or missing so it can't be used, and just
assuming \177 may be wrong.
