Prefer enum glyph_row_area to int where appropriate.

Prefer enum glyph_row_area to int where appropriate.
* dispextern.h (enum glyph_row_area): Add ANY_AREA member.
Fix comment.
(window_box, window_box_width, window_box_left, window_box_left_offset)
(window_box_right, window_box_right_offset): Adjust prototypes.
* xdisp.c (window_box, window_box_width, window_box_left)
(window_box_left_offset, window_box_right, window_box_right_offset):
Use enum glyph_row_area.  Adjust users and tweak comment where needed.
(window_box_edges): Likewise.  Lost 2nd arg since it is always ANY_AREA.
* nsterm.m (ns_clip_to_row):
* w32term.c (w32_clip_to_row):
* xterm.c (x_clip_to_row): Likewise.