(Vdos_unsupported_char_glyph): New variable.

(Vdos_unsupported_char_glyph): New variable.
(syms_of_msdos): DEFVAR_LISP it.
(IT_insert_glyphs, IT_delete_glyphs): New functions which abort
Emacs.
(internal_terminal_init): Set up insert_glyphs_hook and
delete_glyphs_hook to call them.  Explicitly set char_ins_del_ok
to 0.
(unibyte_display_via_language_environment): New variable.
(syms_of_msdos): Devfar it.
(IT_write_glyphs): Honor glyph aliasing via Vglyph_table.
Encode the character codes of the glyphs according to the
terminal_coding in effect.