* xdisp.c (redisplay_internal): Reset tty's color_mode when switching

* xdisp.c (redisplay_internal): Reset tty's color_mode when switching
to another frame.
* frame.c (do_switch_frame): Refine the top_frame/async_visible code.
Don't call set_tty_color_mode.
(store_frame_param): Reset previous_frame rather than call
set_tty_color_mode.
* term.c (set_tty_color_mode): Rewrite.
* dispextern.h (set_tty_color_mode): New type.
* termchar.h (struct tty_display_info): Add `previous_color_mode'.