fixed refresh of addressbook folder contents.
fixed a bug of addressbook that multiple selection with Ctrl key didn't work with GTK+ 2.6.9.
modified several alerts, and added accelerators for the buttons.
added G_ALERTCANCEL to AlertValue, and return it if cancelled.
fixed Turkish locale problem.
reimplemented summary view with GtkTreeView.
replaced intl.h with glib/gi18n.h.
use GTK stock button for button set.
Initial import of Sylpheed (GTK2 version).