Be more careful if selected window shows the buffer other than current,

Be more careful if selected window shows the buffer other than current,
use window_outdated only if this is not so.  This change should also
address some weird issues discussed in Bug#13012.
* window.h (window_outdated): New prototype.
* window.c (window_outdated): Now here.  Convert from static and
always assume window's buffer.
(Fwindow_end, Fwindow_line_height): Use it.
* xdisp.c (reconsider_clip_changes): Remove prototype, drop 2nd arg
and always assume window's buffer.
(redisplay_window): Adjust user.
(redisplay_internal): Call to reconsider_clip_change once and
check whether mode line should be updated only if selected window
shows current buffer.
(run_window_scroll_functions): Use eassert for debugging check.
(Fmove_point_visually, note_mouse_highlight): Use window_outdated.