Include <strings.h>.

Include <strings.h>.
(enable_font_backend): Delete it.
(Qfont_spec, Qfont_entity, Qfont_object): New variables.
(CHECK_VALIDATE_FONT_SPEC): Delete it.
(PT_PER_INCH, POINT_TO_PIXEL, PIXEL_TO_POINT): Moved to font.h.
(null_string): Delete it.
(null_vector): Make it static.
(font_family_alist): Delete it.
(Qnormal): Extern it.
(QCextra, QClanguage): Delete it.
(QClang, QCavgwidth, QCfont_entity, QCfc_unknown_spec): New
variables.
(font_make_spec, font_make_entity, font_make_object)
(font_intern_prop): Renamed from intern_downcase.  Don't downcase
the string.  Callers changed.
(font_pixel_size): Adjusted for the format change of font-related
objects.
(prop_name_to_numeric, prop_numeric_to_name): Delete them.
(font_style_to_value, font_style_symbolic): New function.
(build_font_family_alist): Delete it.
(font_registry_charsets): Use Fassoc_string instead of
assq_no_quit.
(font_prop_validate_symbol): Don't return null_string.
(font_prop_validate_style): Adjusted for the change of
style-related values in a font vector.
(font_property_table): Delete entries for QClangauge and
QCantialias, add entries for QCavgwidth.
(get_font_prop_index): Delete the 2nd argument FROM.
(font_prop_validate): Arguments changed.
(font_put_extra): Adjusted for the change of font-related objects.
(font_expand_wildcards, font_parse_xlfd, font_unparse_xlfd)
(font_parse_fcname, font_unparse_fcname)
(font_prepare_composition): Likewise.
(font_parse_family_registry): Renamed from font_merge_old_spec.
(otf_open): Delete the 1st arg entity.
(font_otf_capability): Adjusted for the above change.
(font_score): New arg alternate_families.  Adjusted for the change
of font-related objects.
(font_sort_entites): New arg best_only.
(font_symbolic_weight, font_symbolic_slant, font_symbolic_width):
Delete them.
(font_match_p): Check alternate families.
(font_find_object): Delete it.
(font_check_object): New function.
(font_clear_cache): Adjusted for the change of font-related
objects.
(font_delete_unmatched): New arg.
(font_list_entities): Call font_driver->list with a spec that
doesn't specify style-related properties.
(font_matching_entity): Arguments changed.  Caller changed.
(font_open_entity): Adjusted for the change of font-related
objects.
(font_close_object, font_has_char, font_encode_char)
(font_get_name, font_get_spec): Likewise.
(font_spec_from_name, font_clear_prop, font_update_lface): New
functions.
(font_find_for_lface, font_open_for_lface, font_load_for_lface):
(font_prepare_for_face, font_done_for_face, font_open_by_name)
(font_at): Adjusted for the change of font-related objects.
(font_range): New function.
(Ffontp, Ffont_spec, Ffont_get, Ffont_put, Flist_fonts)
(Ffont_xlfd_name): Adjusted for the change of font-related
objects.
(Fcopy_font_spec, Fmerge_font_spec): New function.
(Ffont_family_list): Renamed from list-families.
(Finternal_set_font_style_table): Arguments changed.
(Ffont_fill_gstring, Ffont_shape_text, Fopen_font)
(Ffont_drive_otf, Fquery_font, Ffont_match_p): Adjusted for the
change of font-related objects.
(syms_of_font): Delete "ifdef USE_FONT_BACKEND".  DEFSYM new
symboles.