account_find_all_from_address(): new function that returns the
list of all accounts that are matched in an address.
src/alertpanel.[ch]
alertpanel() now accepts a custom widget
alertpanel_with_widget(): new function that pops up a panel with
a custom widget in it
src/gtkutils.[ch]
gtkut_account_menu_new(): new function that allows the selection
of an account from a list of accounts.
src/messageview.c
Extended Return Receipt notification to select the correct
account and to make a security test on the Delivery-Notification
address which should be the same as the Return-Path