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/gnutls/3.4.nix

@@ -1,11 +1,11 @@
 { callPackage, fetchurl, autoreconfHook, ... } @ args:
 
 callPackage ./generic.nix (args // rec {
-  version = "3.4.5";
+  version = "3.4.6";
 
   src = fetchurl {
     url = "ftp://ftp.gnutls.org/gcrypt/gnutls/v3.4/gnutls-${version}.tar.xz";
-    sha256 = "1bks1zpmhmnkz2v32dd9b44pz6x0a5w4yi9zzwsd0a078vhbi25g";
+    sha256 = "1v109px1sy1s731fnawzdsvggdswmr7ha9q5lid4v8pzgznmkdgy";
   };
 
   # This fixes some broken parallel dependencies

pkgs/development/libraries/gnutls/generic.nix

@@ -1,5 +1,5 @@
 { lib, fetchurl, stdenv, zlib, lzo, libtasn1, nettle, pkgconfig, lzip
-, guileBindings, guile, perl, gmp, autogen, libidn, p11_kit, unbound
+, guileBindings, guile, perl, gmp, autogen, libidn, p11_kit, unbound, libiconv
 , tpmSupport ? false, trousers
 
 # Version dependent args
@@ -31,6 +31,7 @@ stdenv.mkDerivation {
   enableParallelBuilding = !guileBindings;
 
   buildInputs = [ lzo lzip nettle libtasn1 libidn p11_kit zlib gmp autogen ]
+    ++ lib.optional (stdenv.isDarwin) libiconv
     ++ lib.optional (tpmSupport && stdenv.isLinux) trousers
     ++ [ unbound ]
     ++ lib.optional guileBindings guile;