Comment 10 for bug 732572

Ok, I took a quick look at this, and setting a custom wav file does require libesd0 (and hence, esound). That is pretty suboptimal, I wonder if there's another way to do this. Normal system sounds are played via libcanberra, although it dlopen()'s that so it will run on systems without it. We should certainly add a libcanberra recommends to thunderbird