Log Message:
Update mlterm to 3.7.0.

Changes noted in doc/en/ReleaseNote:

ver 3.7.0
* Support OSC 1337. (See http://www.iterm2.com/images.html)
* Support animation gif of OSC 5379 show_picture on MacOSX/cocoa.
* Enable to place configuration files in mlterm.app/mlterm/ on MacOSX/Cocoa.
* Add 'mlfc' tool which automatically generates ~/.mlterm/aafont and \ 
~/.mlterm/font-fb.
* Change the format of ~/.mlterm/*font is changed as follows.
  [Charset] = [Font name];[Size],[Font name];[Size],[Font name];...
  -> [Charset] = [Font name]
* Drop XT_CBLINK (CSI?12h/CSI?12l) support.
* Simplify font configuration of OSC 5379. ('mlcc font USASCII <Font \ 
name>' is available.)
* "CSI 38;2;r;g;b m" and "CSI 48;2;r;g;b m" shows high \ 
colors instead of
  approximate vt 256 colors. "vt_color_mode" / \ 
--vtcolor(=256/high/true) option
  changes the behavior.
* Bug fixes:
  Fix illegal memory access on MacOSX/Cocoa and Android.
  Fix segfault in spliting window on MacOSX/Cocoa. (Enbugged at 3.6.2)