Log Message:
mlterm: update to 3.8.6.

Changes noted in doc/en/ReleaseNote:

ver 3.8.6
* Support preserveAspectRatio option of OSC 1337.
* Support DECRQCRA, CSI 15 t, CSI 16 t, CSI 19 t and OSC 5;Ps;? ST.
* Support framebuffer on FreeBSD(98).
* Add vte 0.52.0 API symbols to libvte compatible library.
* Add --rv / "rv_color" option.
* Add servman.exe which manages the list of servers on win32.
* Add "PrivKey" entry to the ssh connection dialog on win32 and Android.
* Add "SCP" entry to the context menu on Android.
* Drop --servlist / "server_list" option.
* Improve performance of redrawing screen when type_engine=cairo.
* Show box style cursor when the cursor is on a picture or an emoji.
* Modify DECRC to save/restore last-column flag used to control wrapping behavior
  rather than manipulating DECAWM (See https://github.com/mattiase/wraptest and
  https://invisible-island.net/xterm/xterm.log.html#xterm_328)
* Change the default value of ssh_private(public)_key option from
  /sdcard/.ssh/id_rsa(.pub) to /sdcard/.mlterm/id_rsa(.pub) on Android.
* Bug fixes:
  Fix compiling error if ./configure is executed with --with-gui=fb,xlib option.
  Fix disappearing title bar on 'lxde' window manager.
  Fix a bug which disabled to replace system palettes by colors of a wall picture
  (if "use_ansi_colors" option is disabled and visual depth is 4) \ 
since 3.8.4.
  Fix the response strings of OSC 20 and OSC 21.
  Use the background color specified by SGR instead of the default one to draw
  pictures and emojis.