dbus with all the fixin's

I was a bit bored, so I fixed up the marshalling code for mozjs_dbus and now it speaks Unicode. To be fair, my changes were only a couple dozen lines. Credit where credit's due, the XUL and JS stuff is all Eric Butler, and I think most of the C++ is too (though the marshalling code looks nicked from now-defunct DBuzilla). Since it's a JS-centered approach, I think one could rejig the whole C++ component to tap into JS directly (like js-ctypes does). That saves going through nsIVariant, and allows the back-end to chew on the JS objects directly. It would probably simplify the JS slightly as well (it is already a nice, modular design).

And I'm pretending the 3 hours spent looking for the reason why my Fx build didn't pick up the mozjs_dbus extension never happened. (The install.rdf ID field said mozjsdbus. One underscore. Three hours. In theaters now...)