* fix: correct launch of app-started event in Thunderbird when windows not
  actually mapped (or "mapped" to another desktop)
* check app started if -firetrayShowHide or -firetrayPresent

We can't base the app-started event solely on MapNotify, at least because the
app could be started on another desktop (not mapped). The app-started event in
Thunderbird is not based on mail-startup-done events. We might have to consider
implementing a watchdog for unexpected cases...