include weight in listing pattern, instead check weight of each
listed font. Don't include scalable in pattern. Pay attention to
FONT_PIXEL_SIZE_QUANTUM.
(Qsans__serif): New variables.
(ftfont_generic_family_list): New variable.
(syms_of_ftfont): Initialize the above variables.
(ftfont_pattern_entity): Argument NAME deleted.
(ftfont_list_generic_family): New function.
(ftfont_parse_name): Delete this function.
(ftfont_list): Try generic family only when FcFontList found no
font.
(ftfont_list_family): Fix args to FcObjectSetBuild.
font.c.
(ftfont_pattern_entity): New function.
(ftfont_get_cache): Assume that freetype_font_cache is already
initialized.
(ftfont_list): Handle the case that a file is specified in font
name. Use ftfont_pattern_entity to generate entities.
(ftfont_has_char): Check if the pattern contains FC_CHARSET.
(syms_of_ftfont): Initialize freetype_font_cache.
