(Vshow_nonbreak_escape): New lisp var.

(Vshow_nonbreak_escape): New lisp var.
(syms_of_xdisp): DEFVAR_LISP it.
(escape_glyph_face): Remove var.
(redisplay_window): Don't initialize it.
(setup_for_ellipsis, get_next_display_element):
Set it->dpvec_face_id to -1.
(get_next_display_element): Test Vshow_nonbreak_escape.
Do not setup escape_glyph_face.
Properly merge escape-glyph face or face from display table with
current face for escape and control characters.  Set
it->dpvec_face_id to relevant face id instead of adding it to each
element of display vector.
(next_element_from_display_vector): If it->dpvec_face_id is set,
use that instead of lface_id from glyph itself.