Select global font paths for xorg.conf and fontconfig

<xorgconfig>
  <fontpath>
    <value>/opt/emacs/share/emacs/fonts</value>
    <value>/usr/share/fonts/some/other</value>
  </fontpath>
</xorgconfig>

Load config: List, Add (Beginning or End), Remove, Clear
Write out (incrementally)

Will be asked if directory contains nothing but fixed fonts; will add
:unscaled in this case

Regenerate fonts.dir, run fc-cache
