[balsa] (25 commits) Non-fast-forward update to branch popover

[Peter Bloomfield <peterb src gnome org>]

The branch 'popover' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  c67312a... pref-manager: Use GtkPopover for "Add" options

Commits added to the branch:

  29b9285... mailbox: when closing a mailbox, remove source (*)
  547eb5a... main-window: Really disconnect signal (*)
  a9bbd48... mailbox: Check whether the mailbox was closed (*)
  d9b18d2... Guard against mailbox changes (*)
  fce9bdf... mailbox: Fix thinko (*)
  179dbfe... mailbox-local: Check for error return value (*)
  8e6b6cc... mailbox: Check for finalized mailbox (*)
  266cf2c... mailbox: Ensure gboolean return value (*)
  e556a72... Stop using gtk_main_iteration_do() (*)
  5a77fe5... balsa-index: Use a single bit for 'expanded' (*)
  5cd4f9b... mailbox: If priv->mindex is NULL, try again later (*)
  84bfb01... mailbox-local: Set messages-threaded (*)
  109364d... balsa-index: cleanup (*)
  7f457d6... balsa-index: Use a low priority idle handler (*)
  90f8b55... main-window: Drop another guard (*)
  90ee8bc... Move some more code to a thread (*)
  43264bc... Fix a few bugs (*)
  7a01d8d... mailbox-local: Set messages-loaded (*)
  1a4bd3c... mailbox-local: Fix a thinko (*)
  63d072d... Revert 90ee8bcc82d8ebdae0bd286212c21d1138531658 (*)
  e15cad4... balsa-index: Use gtk_tree_view_expand_to_path() (*)
  9cbcd3c... balsa-index: improve expand and collapse (*)
  e466beb... balsa-index: Fix the previous commit (*)
  2aa7395... balsa-index: Simplify managing handlers (*)
  8e3679c... pref-manager: Use GtkPopover for "Add" options

(*) This commit already existed in another branch; no separate mail sent