Add pre-redisplay-function and rectangular region
* lisp/rect.el: Use lexical-binding. Add new rectangular region support.
(rectangle-mark): New command.
(rectangle--region): New var.
(deactivate-mark-hook): Reset rectangle--region.
(rectangle--extract-region, rectangle--insert-for-yank)
(rectangle--highlight-for-redisplay)
(rectangle--unhighlight-for-redisplay): New functions.
(region-extract-function, redisplay-unhighlight-region-function)
(redisplay-highlight-region-function): Use them to handle
rectangular region.
* lisp/simple.el (region-extract-function): New var.
(delete-backward-char, delete-forward-char, deactivate-mark): Use it.
(kill-new, kill-append): Remove obsolete `yank-handler' argument.
(kill-region): Replace obsolete `yank-handler' arg with `region'.
(copy-region-as-kill, kill-ring-save): Add `region' argument.
(redisplay-unhighlight-region-function)
(redisplay-highlight-region-function): New vars.
(redisplay--update-region-highlight): New function.
(pre-redisplay-function): Use it.
(exchange-point-and-mark): Don't deactivate the mark before
reactivate-it anyway.
* lisp/comint.el (comint-kill-region): Remove yank-handler argument.
* lisp/delsel.el (delete-backward-char, backward-delete-char-untabify)
(delete-char): Remove property, since it's now part of their
default behavior.
(self-insert-iso): Remove property since this command doesn't exist.
* src/xdisp.c (prepare_menu_bars): Call Vpre_redisplay_function.
(syms_of_xdisp): Declare pre-redisplay-function.
(markpos_of_region): Remove function.
(init_iterator, compute_stop_pos, handle_face_prop)
(face_before_or_after_it_pos, reseat_to_string)
(get_next_display_element, window_buffer_changed)
(redisplay_internal, try_cursor_movement, redisplay_window)
(try_window_reusing_current_matrix, try_window_id, display_line)
(note_mode_line_or_margin_highlight, note_mouse_highlight)
(display_string, mouse_face_from_buffer_pos): Remove region handling.
* src/window.h (struct window): Remove field `region_showing'.
* src/dispextern.h (struct it): Remove region_beg/end_charpos.
(face_at_buffer_position, face_for_overlay_string)
(face_at_string_position): Update prototypes.
* src/xfaces.c (face_at_buffer_position, face_for_overlay_string)
(face_at_string_position): Remove `region_beg' and `region_end' args.
* src/fontset.c (Finternal_char_font):
* src/font.c (font_at, font_range): Adjust calls accordingly.
* src/insdel.c (Qregion_extract_function): New var.
(syms_of_insdel): Initialize it.
(prepare_to_modify_buffer_1): Use it.