Split some GTK/X11-related packages

The closure of the Pan newsreader is now down from 344 MiB to 195 MiB.

pkgs/development/libraries/pango/1.29.x.nix

@@ -8,14 +8,16 @@ stdenv.mkDerivation rec {
     sha256 = "0zqjq6ccv6mbah74rcvb03ksq1jwan21z37mdmqa56307sax3s3s";
   };
 
+  enableParallelBuilding = true;
+
+  outputs = [ "dev" "out" "bin" "doc" ];
+
   buildInputs = stdenv.lib.optional stdenv.isDarwin gettext;
 
   buildNativeInputs = [ pkgconfig ];
 
   propagatedBuildInputs = [ x11 glib cairo libpng ];
 
-  postInstall = "rm -rf $out/share/gtk-doc";
-
   meta = {
     description = "A library for laying out and rendering of text, with an emphasis on internationalization";