(close_ft): Check ft_info->ft_face and work

(close_ft): Check ft_info->ft_face and work
differently.
(add_font_info): Allocate ft_info by M17N_OBJECT.
(ft_close): Delete it.
(mfont__ft_driver): Don't set ft_close.
(ft_select): Increment ref-count of best_font.
(ft_open): Decremented ref-count of base.  On error, call
FT_Done_Face and free ft_info.
(ft_find_metric): Always use XXX_MONO in load_flags.
(ft_render): Fix setting of width.  Call
frame->driver->draw_points instead of mwin__draw_points.
(ft_to_prop): Don't set mfont__driver_list.
(mfont__ft_fini): Just unref ft_info.