action.c: fixed a bug that inserted text was always placed at the top.
action.c: fixed wrong insertion point at TextView.
enabled compilation with MinGW.
fix invalid iterator warnings of action.
modified IO dialog of action.
replaced intl.h with glib/gi18n.h.
action.c: don't include header part in message text.
use GTK stock button for button set.
action.c: convert locale strings to UTF-8 before displaying it.
Initial import of Sylpheed (GTK2 version).