data/fonts: cleanup

* 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

pkgs/data/fonts/stix-otf/default.nix

@@ -1,11 +1,11 @@
-{stdenv, fetchzip}:
+{ lib, fetchzip }:
 
 let
   version = "1.1.1";
 in fetchzip rec {
   name = "stix-otf-${version}";
 
-  url = "mirror://sourceforge/stixfonts/STIXv${version}-word.zip";
+  url = "http://ftp.fi.muni.cz/pub/linux/gentoo/distfiles/STIXv${version}-word.zip";
 
   postFetch = ''
     mkdir -p $out/share/fonts
@@ -14,7 +14,7 @@ in fetchzip rec {
 
   sha256 = "04d4qxq3i9fyapsmxk6d9v1xirjam8c74fyxs6n24d3gf2945zmw";
 
-  meta = with stdenv.lib; {
+  meta = with lib; {
     homepage = http://www.stixfonts.org/;
     description = "Fonts for Scientific and Technical Information eXchange";
     license = licenses.ofl;