Cache current header and mode line height for each window.

Cache current header and mode line height for each window.
* window.h (struct window): New fields mode_line_height
and header_line_height.
* window.c (make_window): Initialize them.
* dispextern.h (CURRENT_MODE_LINE_HEIGHT)
(CURRENT_HEADER_LINE_HEIGHT): Use them.  Adjust comment.
(current_mode_line_height, current_header_line_height):
Remove declaration.
* xdisp.c (current_mode_line_height, current_header_line_height):
Remove.
(pos_visible_p, init_xdisp): Adjust user.
(redisplay_window): Invalidate mode_line_height and
header_line_height if current and desired matrices do not agree.