Avoid some portability problems by eschewing 'extern inline' functions.

Avoid some portability problems by eschewing 'extern inline' functions.

The trivial performance wins aren't worth the portability hassles; see
<http://lists.gnu.org/archive/html/emacs-devel/2011-11/msg00084.html>
et seq.
* dispextern.h (window_box, window_box_height, window_text_bottom_y)
(window_box_width, window_box_left, window_box_left_offset)
(window_box_right, window_box_right_offset): Undo previous change,
by removing the "extern"s.
* intervals.c (adjust_intervals_for_insertion)
(adjust_intervals_for_deletion): Undo previous change,
making these static again.
(offset_intervals, temp_set_point_both, temp_set_point)
(copy_intervals_to_string): No longer inline.
* xdisp.c (window_text_bottom_y, window_box_width)
(window_box_height, window_box_left_offset)
(window_box_right_offset, window_box_left, window_box_right)
(window_box): No longer inline.