hterm: strip most control chars out for bracketed paste
hterm: strip most control chars out for bracketed paste

Since xterm strips out control chars (other than whitespace ones) from
the paste buffer when bracketed paste is enabled, do the same in hterm.
This makes it a bit more robust in case the buffer happens to have its
own escape sequences (including the closing \e[201~).

Change-Id: Id773958ffc580850e5d4846278f1e1e893b92f4f
Reviewed-on: https://chromium-review.googlesource.com/958294
Reviewed-by: Vitaliy Shipitsyn <6f51537d61e46a00bf958b60dbef5b5870c2bf22@google.com>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>

chromium/hterm,chromium/hterm,chromium/hterm,chromium/hterm