Avoid looping over all frame windows to freeze and unfreeze.

Avoid looping over all frame windows to freeze and unfreeze.
* window.h (struct window): Drop frozen_window_start_p.
(freeze_window_starts): Drop prototype.
* frame.h (struct frame): New frozen_window_starts flag.
(FRAME_WINDOWS_FROZEN): New macro.
* window.c (freeze_window_start, freeze_window_starts):
Remove.
(select_window, replace_window): Adjust users.
* xdisp.c (resize_mini_window): Use FRAME_WINDOWS_FROZEN.
(window_frozen_p): New function.
(redisplay_window): Use it.