* make font derivations fixed-output where applicable
* fix dead links
* `stdenv.lib` -> `lib` where `stdenv` is not involved
* remove `meta.platforms = [ unix ]` and `meta.platforms = [ linux ]` because the restriction has no sense for data packages
With this change they now use `stdenv.mkDerivation` instead. Also some
minor cleanups such as URL fixes, adding version numbers, adding
descriptions, etc.
