Merge staging into closure-size

The most complex problems were from dealing with switches reverted in
the meantime (gcc5, gmp6, ncurses6).
It's likely that darwin is (still) broken nontrivially.

pkgs/development/libraries/libsodium/default.nix

@@ -1,11 +1,11 @@
 { stdenv, fetchurl }:
 
 stdenv.mkDerivation rec {
-  name = "libsodium-1.0.3";
+  name = "libsodium-1.0.6";
 
   src = fetchurl {
     url = "https://download.libsodium.org/libsodium/releases/${name}.tar.gz";
-    sha256 = "120jkda2q58p0n68banh64vsfm3hgqnacagj425d218cr4ycdkyb";
+    sha256 = "0ngvcjwg6m9nivzi208yvz8yvmk6kxnvyr25w907kaicgpm063cl";
   };
 
   outputs = [ "dev" "out" ];