Clean up cairo printing code

Clean up cairo printing code

* src/gtkutil.c (xg_get_page_setup): Use listn.
* src/xfns.c (Fx_export_frames, Fx_print_frames_dialog): Doc fix.  Use
decode_window_system_frame and FRAME_VISIBLE_P.
(Fx_print_frames_dialog): Use redisplay_preserve_echo_area instead
of Fdisplay.
* src/xterm.c (x_cr_export_frames): Use redisplay_preserve_echo_area
instead of Fdisplay.  Temporarily unblock_input around QUIT.