Add transition code to read old header choices

	* src/sendmsg-window.c (init_menus): add transition code to read
	old message header choices.
Set gpg mode correctly

	* src/sendmsg-window.c (bsmsg_setup_gpg_ui_by_mode): set gpg
	mode correctly.
Fix action name

	* src/sendmsg-window.c (sendmsg_window_continue): fix action
	name.
Disconnect handler when toolbar is destroyed

	* src/toolbar-factory.c (tm_toolbar_weak_notify): disconnect
	model's "changed" signal handler when toolbar is destroyed.