The following changes consolidates the fringe handling from

The following changes consolidates the fringe handling from
xterm.c, w32term.c, and macterm.c into xdisp.c.

* xdisp.c: Consolidate fringe handling code here.
(left_bits, right_bits, continued_bits, continuation_bits)
(ov_bits, zv_bits): Define fringe bitmaps.
(fringe_bitmaps): New array holding fringe bitmaps.
(draw_fringe_bitmap): Draw a specific bitmap; call display
specific drawing routine via rif->draw_fringe_bitmap.
(draw_row_fringe_bitmaps): Generic replacement for
x_draw_row_fringe_bitmaps; all callers changed.
(compute_fringe_widths): Generic replacement for
x_compute_fringe_widths; all callers changed.