Substantial rewrite for new redisplay. Major changes:

Substantial rewrite for new redisplay. Major changes:
Skeleton support for images, toolbars, tooltips from xfns.c.
(Fx_create_frame): Use system default for default scroll bar width.
(w32_get_arg): Renamed from x_get_arg.
(Fx_file_dialog): New function.
(w32_list_fonts): Check cache before asking system.
(Vw32_enable_synthesized_fonts): New variable.
(Vw32_enable_italics): Obsolete, removed.