Merge branch 'master' into closure-size

TODO: there was more significant refactoring of qtbase and plasma 5.5
on master, and I'm deferring pointing to correct outputs to later.

pkgs/development/libraries/libpng/12.nix

@@ -3,11 +3,11 @@
 assert !(stdenv ? cross) -> zlib != null;
 
 stdenv.mkDerivation rec {
-  name = "libpng-1.2.54";
+  name = "libpng-1.2.55";
 
   src = fetchurl {
     url = "mirror://sourceforge/libpng/${name}.tar.xz";
-    sha256 = "0wnjy7gqn0f24qrlggs7kl0ij59by413j1xmqp12n3vqh9j531fg";
+    sha256 = "0zkra0b9lrpk2axassdgkqinmc2ba6b473sm52xbpyknaqs2fljy";
   };
 
   outputs = [ "dev" "out" "man" ];

pkgs/development/libraries/libpng/default.nix

@@ -3,11 +3,11 @@
 assert zlib != null;
 
 let
-  version = "1.6.19";
-  sha256 = "1s1mmkl79ghiczi2x2rbnp6y70v4c5pr8g3icxn9h5imymbmc71i";
+  version = "1.6.20";
+  sha256 = "12wis4rlisfnw79pj2778m42m94xpi9nq8m385hxk11lkyg9biam";
   patch_src = fetchurl {
     url = "mirror://sourceforge/libpng-apng/libpng-${version}-apng.patch.gz";
-    sha256 = "0bgqkac16yhl0zwjzq2zwkixg2l2x3a6blbk3k0wqz0lza2a6jrh";
+    sha256 = "11xgal9qk6fmqdgcb37xg55f2y58wizszw54p1pyq855d2xpwfz6";
   };
   whenPatched = stdenv.lib.optionalString apngSupport;