New versions of Firebug are not detected

[rensatsu]

It seems that new versions of Firebug doesn't modify 'window' object with 'Firebug', so it's useless to check for 'window.Firebug'. It instead adds new function called 'window.console.exception' which can be used for detection.

[sindresorhus]

It will still detect Firebug when it's docked. Also window.console.exception seems to be available even when Firebug is not open though, so can't really use that. Other suggestions welcome :)