Review and drop old frame resize hack.

Review and drop old frame resize hack.
* frame.h (struct frame): Remove force_flush_display_p.
* dispnew.c (update_frame): Adjust user and don't call
flush_frame here.  The comment has said that there was an issues
with redisplaying fringes, but I don't see any differences with
and without this hack.  Hopefully we can continue without it.
* xdisp.c (clear_garbaged_frames): Adjust user and do not clear
current frame matrices twice if resized_p is set.