GTK-based timer in ATS2

I implemented a timer yesterday:

https://github.com/githwxi/ATS-Postiats/blob/master/contrib/libats-hwxi/teaching/myGTK/TEST/test_gtkcairotimer.dats

I intend to use this timer to control a simple game (something for the
class I am teaching).
There is nothing fancy. Just want to show that this sort of thing can be
readily done in ATS. Because of the use of templates
in this implementation, adaptation can be added with relative ease.

Cheers!

–Hongwei