Add "account-status-changing" signal from instantbird
It's like "account-status-changed", but emitted before the status change
instead of after.
Instantbird ticket: https://bugzilla.mozilla.org/show_bug.cgi?id=954403
Add "buddy-remove-from-group" blist signal from instantbird
It is fired when a buddy is removed permanently from a group but
not from the buddy list. (ie when the buddy has been moved)
Just getting warmed up! Starting with the easiest part - I don't actually care about these signals but they were trivial to cherry pick.
Wow, how have we never needed these before... :)