Merge branch 'master' into staging-next

There ver very many conflicts, basically all due to
name -> pname+version.  Fortunately, almost everything was auto-resolved
by kdiff3, and for now I just fixed up a couple evaluation problems,
as verified by the tarball job.  There might be some fallback to these
conflicts, but I believe it should be minimal.

Hydra nixpkgs: ?compare=1538299

pkgs/applications/video/shotcut/default.nix

@@ -7,13 +7,13 @@ assert stdenv.lib.versionAtLeast mlt.version "6.8.0";
 
 mkDerivation rec {
   pname = "shotcut";
-  version = "19.07.15";
+  version = "19.08.16";
 
   src = fetchFromGitHub {
     owner = "mltframework";
     repo = "shotcut";
     rev = "v${version}";
-    sha256 = "0drl0x8x45kysalzx1pbg0gkvlxaykg9zka1fdkrl4iqfs4s7vv2";
+    sha256 = "0alnnfgimfs8fjddkcfx4pzyijwz5dgnqic5qazaza6f4kf60801";
   };
 
   enableParallelBuilding = true;