* window.h (struct window): Convert base_line_number, base_line_pos

* window.h (struct window): Convert base_line_number, base_line_pos
and column_number_displayed members from Lisp_Object to ptrdiff_t.
Convert region_showing member from Lisp_Object to bitfield.
Remove sequence_number member.  Adjust comments.
* window.c (sequence_number): Remove.
(make_window): Initialize column_number_displayed.
* print.c (print_object): Follow the printed representation of
frames and print window pointer to distinguish between windows.
(adjust_window_count): Invalidate base_line_pos.  Adjust comment.
* xdisp.c (wset_base_line_number, wset_base_line_pos)
(wset_column_number_displayed, wset_region_showing): Remove.
(window_buffer_changed, mode_line_update_needed, redisplay_internal)
(try_scrolling, try_cursor_movement, redisplay_window)
(try_window_reusing_current_matrix, try_window_id, display_line)
(display_mode_lines, decode_mode_spec): Adjust users.
* .gdbinit (pwinx): Do not print sequence_number.