emulation: Deccolm mode switch clears the screen and moves cursor home

https://bugzilla.gnome.org/show_bug.cgi?id=731155#c6
emulation: Fix cursor handling at right margin

https://bugzilla.gnome.org/show_bug.cgi?id=731155
widget: Fix box drawing characters in wide CJK mode
widget: Narrow the set of word chars

https://bugzilla.gnome.org/show_bug.cgi?id=730632