Getting whether it's Tango or Phobos

[Robert Fraser]

Is there a reliable way to deduce whether the user is using Tango or 
Phobos? I used to use:

static if(is(typeof(object.toUtf8)))

But since that got changed to toString that doesn't work right now. For 
the time being, I can verify it's D1 and then use (with Tango 0.99.6)

static if(!is(typeof(string)))

But I'm guessing Tango may be given a string type soon...?