Checking of FONT_DEBUG is moved to font.h. All calls of

Checking of FONT_DEBUG is moved to font.h.  All calls of
xassert are changed to font_assert.  Many unused variables
deleted.
(Vfont_weight_table, Vfont_slant_table, Vfont_width_table): New
variables.
(struct table_entry): Moved from xfaces.c and modified.
(weight_table, slant_table, width_table): Moved from xfaces.c and
contents adjusted for the change of struct table_entry.
(font_style_to_value, font_style_symbolic): Adjuted for the format
change of font_style_table.
(font_parse_family_registry): Don't overwrite existing foundry and
family of font_spec.
(font_score): Fix calculation of diff for sizes.
(font_sort_entites): Call font_add_log.
(font_delete_unmatched): Return a newly created list.
(font_list_entities): Fix previous change.  Call font_add_log.
(font_matching_entity, font_open_entity, font_close_entity): Call
font_add_log.
(Ffont_xlfd_name): New arg FOLD-WILDCARDS.
(Finternal_set_font_style_table): Deleted.
(BUILD_STYLE_TABLE): New macro.
(build_style_table): New function.
(Vfont_log, font_log_env_checked): New variables.
(font_add_log): New function.
(syms_of_font): Delete defsubr Sinternal_set_font_style_table.
Declare Lisp variables "font-weight-table", "font-slant-table",
"font-width-table", and "font-log".  Initialize font_style_table.