made query-password function UI independent.
separated trayicon into another module, and notify new messages with trayicon on receive.
added wrappers for C library function that take pathname arguments.
enabled compilation with MinGW.
added an option to execute command when new messages arrived.
integrated junk filter setting into common prefs.
reimplemented progress dialog with GtkTreeView.
fixed a transient window problem.
reimplemented summary view with GtkTreeView.
modified ProgressDialog to use GtkDialog.
replaced intl.h with glib/gi18n.h.
removed a warning.
use GTK stock button for dialog button set.
Initial import of Sylpheed (GTK2 version).