eta authored Apr 27, 2020 and eta committed Aug 11, 2020

- This prevents 30-60 second lockups when starting gajim while the main thread
  is processing large numbers of incoming stanzas and not yielding to the GTK
  main loop at all.
- This is done by explicitly running the main loop after a stanza is received,
  if there are events pending.

(Empirically, this makes gajim actually usable on my machine, whereas current
master is pretty bad lockup-wise after startup/reconnection...)