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/tools/compression/xz/default.nix

@@ -1,11 +1,11 @@
 { stdenv, fetchurl }:
 
 stdenv.mkDerivation rec {
-  name = "xz-5.2.1";
+  name = "xz-5.2.2";
 
   src = fetchurl {
     url = "http://tukaani.org/xz/${name}.tar.bz2";
-    sha256 = "101a1kih58s1ysqfncqw69qnwx1zlbjxwhnfmp0z5gz0jzs4i4b7";
+    sha256 = "1da071wyx921pyx3zkxlnbpp14p6km98pnp66mg1arwi9dxgbxbg";
   };
 
   outputs = [ "dev" "out" "bin" "man" "doc" ];