Refine redisplay optimizations to only redisplay *some* frames/windows
rather than all of them.
* src/xdisp.c (REDISPLAY_SOME): New constant.
(redisplay_other_windows, wset_redisplay, fset_redisplay)
(bset_redisplay, bset_update_mode_line): New functions.
(message_dolog): Use bset_redisplay.
(clear_garbaged_frames): Use fset_redisplay.
(echo_area_display): Use wset_redisplay.
(buffer_shared_and_changed): Remove.
(prepare_menu_bars): Call Vpre_redisplay_function before updating
frame titles. Compute the actual set of windows redisplayed.
Don't update frame titles and menu bars for frames that don't need to
be redisplayed.
(propagate_buffer_redisplay): New function.
(AINC): New macro.
(redisplay_internal): Use it. Be more selective in the set of windows
we redisplay. Propagate windows_or_buffers_changed to
update_mode_lines a bit later to simplify the code.
(mark_window_display_accurate_1): Reset window and buffer's
`redisplay' flag.
(redisplay_window): Do nothing if neither the window nor the buffer nor
the frame needs redisplay.
* src/window.h (struct window): Add `redisplay' field.
(wset_redisplay, fset_redisplay, bset_redisplay, bset_update_mode_line)
(redisplay_other_windows, window_list): New declarations.
* src/window.c (select_window, Fset_window_start): Use wset_redisplay.
(window_list): Not static any more.
(grow_mini_window, shrink_mini_window): Use fset_redisplay.
* src/minibuf.c (read_minibuf_unwind): Don't redisplay everything.
* src/insdel.c (prepare_to_modify_buffer_1): Use bset_redisplay.
* src/frame.c (Fmake_frame_visible): Don't redisplay everything.
* src/frame.h (struct frame): Add `redisplay' field.
Move `external_menu_bar' bitfield next to other bit-fields.
(SET_FRAME_GARBAGED): Use fset_redisplay.
(SET_FRAME_VISIBLE): Don't garbage the frame;
Use redisplay_other_windows.
* src/buffer.h (struct buffer): Add `redisplay' field.
* src/buffer.c (Fforce_mode_line_update): Pay attention to the `all' flag.
(modify_overlay): Use bset_redisplay.
* src/alloc.c (gc_sweep): Don't unmark strings while sweeping symbols.