Add millisecond precision to epoch timestamps

[jcnmsg]

Date.now(), performance.now() and new Date().getTime() now return a proper timestamp in milliseconds. I edited the fallback function provided by Duktape and kept referencing an external clock for the milliseconds themselves. Not sure if it's the best approach so let me know what you think.

Closes #3

To verify it's working:

Display.setVSync(true);
Font.fmLoad()

while(1){
    Display.clear(Color.new(0,0,0)) ;
    Font.fmPrint(10, 10, .5, "Milliseconds elapsed since the epoch: " + Date.now(), Color.new(255, 255, 255));
    Display.flip();
}

[DanielSant0s]

Looks good to me, I haven't had much time recently, I saw that you registered the issue but I couldn't find a space in my daily routine to see a way to solve it, I'm glad you took the initiative, thank you so much. Merging RN