Merge 'staging' into closure-size

- there were many easy merge conflicts
- cc-wrapper needed nontrivial changes

Many other problems might've been created by interaction of the branches,
but stdenv and a few other packages build fine now.

pkgs/development/libraries/gdk-pixbuf/default.nix

@@ -2,15 +2,15 @@
 , jasper, libintlOrEmpty, gobjectIntrospection }:
 
 let
-  ver_maj = "2.30";
-  ver_min = "8";
+  ver_maj = "2.31";
+  ver_min = "3";
 in
 stdenv.mkDerivation rec {
   name = "gdk-pixbuf-${ver_maj}.${ver_min}";
 
   src = fetchurl {
     url = "mirror://gnome/sources/gdk-pixbuf/${ver_maj}/${name}.tar.xz";
-    sha256 = "1gpqpskp4zzf7h35bp247jcvnk6rxc52r69pb11v8g8i2q386ls8";
+    sha256 = "ddd861747bb7c580acce7cfa3ce38c3f52a9516e66a6477988fd100c8fb9eabc";
   };
 
   outputs = [ "dev" "out" "bin" "doc" ];