Get recent bad certs

@daveschaefer: from [short guide on the proper way to get the exceptions dialog](https://bugzilla.mozilla.org/show_bug.cgi?id=1025332#c11) we are apparently supposed to retrieve the nsITransportSecurityInfo and hence the SSLState in the onSecurityChange() method of nsIWebProgressListener. Could you please verify if this works as intended! I chose to implement this a hotfix as I might find a cleaner way with all the tabinfo_restructuring anyway (maybe it's already implemented, I don't remember) which makes heavy use of the nsIWebProgressListener functionality.