libxnd, pythonPackages.xnd: unstable-2018-11-27 -> unstable-2019-08-01

this is the most recent commit to upstream's master at time of writing

includes fixes of python package for darwin

pkgs/development/libraries/libxnd/default.nix

@@ -6,13 +6,13 @@
 
 stdenv.mkDerivation {
   pname = "libxnd";
-  version = "unstable-2018-11-27";
+  version = "unstable-2019-08-01";
 
   src = fetchFromGitHub {
-    owner = "plures";
+    owner = "xnd-project";
     repo = "xnd";
-    rev = "8a9f3bd1d01d872828b40bc9dbd0bc0184524da3";
-    sha256 = "10jh2kqvhpzwy50adayh9az7z2lm16yxy4flrh99alzzbqdyls44";
+    rev = "6f305cd40d90b4f3fc2fe51ae144b433d186a6cc";
+    sha256 = "1n31d64qwlc7m3qkzbafhp0dgrvgvkdx89ykj63kll7r1n3yk59y";
   };
 
   buildInputs = [ libndtypes ];
@@ -28,6 +28,14 @@ stdenv.mkDerivation {
       "--with-libs=${libndtypes}/lib"
   ];
 
+  # other packages which depend on libxnd seem to expect overflow.h, but
+  # it doesn't seem to be included in the installed headers. for now this
+  # works, but the generic name of the header could produce problems
+  # with collisions down the line.
+  postInstall = ''
+    cp libxnd/overflow.h $out/include/overflow.h
+  '';
+
   doCheck = true;
 
   meta = {