ver 3.1.3
* Support OSC 5;0 and OSC 5;1.
* Support CSI ? 8840 h, CSI ? 8840 l and CSI ? 8840 n.
  (see https://docs.google.com/document/d/1Dgq81J0eQEfjq3MR__O7VrbSVnatr9CCqMEITse9psk/edit?pli=1)
* Support CSI SP q partially.
* Support CSI [>4;2 m and CSI [>4;0m partially.
  (Note that sequence from terminal is CSI [<code>;<mod>u, not CSI [27;<mod>;<code>~.)
* Add "ssh_keepalive_interval" option.
* Add "ssh_x11_forwarding" option.
* Add "use_bold_font" option.
* Add "use_local_echo" option and CSI ? 9500 h / CSI ? 9500 l which enable or disable
  local echo mode.
* Merge SF patches:
  #3529392 (Thanks to Ahmed El-Mahmoudy)
  #3529386 (Thanks to Ahmed El-Mahmoudy)
  #3530235 (Thanks to Ahmed El-Mahmoudy)
* Bug fixes:
  #3528838 (Thanks to Thomas Wolff)
  #3528836 (Thanks to Thomas Wolff)
  Fix a bug which wrongly keeps a screen which has failed to open.
  Show characters in the center of cells whose width is larger than the default.
  (Thanks to Andi Cristian Serbanescu)
  Fix a bug which erases scrolled area. (Thanks to Andi Cristian Serbanescu)
  Fix failure of opening pty in startup in MacOS 10.7.
  (Thanks to saitoha san)