bug#26618: Add 0ad

[Clément Lassieur]

Theses patches add 0ad and mozjs-38 (a dependency).  I worked in
cooperation with ng0.

0ad needs a window manager that supports 'Extended Window Manager
Hints'.  See https://en.wikipedia.org/wiki/Extended_Window_Manager_Hints
for a list.

I did not try multiplayer mode.  I ran it with Awesome WM, so I did not
test the icons and desktop things: I'm not sure about it.

Please let me know if you see anything wrong :)