hterm: support xterm beam cursor shapes
hterm: support xterm beam cursor shapes

BUG=chromium:331617

Change-Id: Ie7e1cf9cae38242143084b5375482db5323f4e86
Reviewed-on: https://chromium-review.googlesource.com/490769
Reviewed-by: Brandon Gilmore <adbfbaf7e4f927b45ce8ad3e5043a632414a833b@google.com>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>

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