Window-related stuff cleanup here and there.

Window-related stuff cleanup here and there.
* dispnew.c (Finternal_show_cursor, Finternal_show_cursor_p):
Use decode_any_window.
* fringe.c (Ffringe_bitmaps_at_pos): Likewise.
* xdisp.c (Fformat_mode_line): Likewise.
* font.c (Ffont_at): Use decode_live_window.
* indent.c (Fcompute_motion, Fvertical_motion): Likewise.
* window.c (decode_next_window_args): Likewise.
(decode_any_window): Remove static.
* window.h (decode_any_window): Add prototype.
* lisp.h (CHECK_VALID_WINDOW, CHECK_LIVE_WINDOW): Move from here...
* window.h: ...to here, redefine via WINDOW_VALID_P and WINDOW_LIVE_P,
respectively.