Improve / cleanup namelang matching

Previously, if the patten didn't request, eg, style, then the style
and stylelang were fully copied from the font, even though the pattern
had a stylelang.  Eg:

$ fc-match 'Apple Color Emoji:stylelang=en'
Apple Color Emoji.ttf: "Apple Color Emoji" "標準體"

This change both fixes that and makes the code much more readable.  Now:

$ fc-match 'Apple Color Emoji:stylelang=en'
Apple Color Emoji.ttf: "Apple Color Emoji" "Regular"