[Fontconfig] Font priority and locale settings

[Eric Sagnes]

Hi,

I noticed that `fc-match` result is influenced by locale settings.

For example with the following configuration snippet:

```
  <alias>
    <family>serif</family>
    <prefer>
      <family>DejaVu Serif</family>
      <family>IPAPMincho</family>
      <family>Baekmuk Batang</family>
    </prefer>
  </alias>
```

If the locale is `en_US.UTF8`, `DejaVu Serif` will be correctly matched as the default font:

```
$ LANG=en_US.UTF8 fc-match serif -s | head -n 5
DejaVuSerif.ttf: "DejaVu Serif" "Book"
DejaVuSerif-Bold.ttf: "DejaVu Serif" "Bold"
DejaVuSerif-Italic.ttf: "DejaVu Serif" "Italic"
DejaVuSerif-BoldItalic.ttf: "DejaVu Serif" "Bold Italic"
ipamp.ttf: "IPAPMincho" "Regular"
```

On the other hand, if the locale is set to `ja_JP.UTF8`, `IPAPMincho` font will be preferred over `DejaVu Serif`:

```
$ LANG=ja_JP.UTF8 fc-match serif -s | head -n 5
ipamp.ttf: "IPA P明朝" "Regular"
DejaVuSerif.ttf: "DejaVu Serif" "Book"
DejaVuSerif-Bold.ttf: "DejaVu Serif" "Bold"
DejaVuSerif-Italic.ttf: "DejaVu Serif" "Italic"
DejaVuSerif-BoldItalic.ttf: "DejaVu Serif" "Bold Italic"
```

Is this an expected behavior?
In this case, is there a way to have the preferred order respected unregarding of locale settings?

Cheers,

-- 
Eric Sagnes
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