Turn more licenses into lib.licenses style

Should eval cleanly, as far as -A tarball tells me.

Relevant: issue #2999, issue #739

pkgs/tools/networking/netkit/tftp/default.nix

@@ -19,7 +19,7 @@ stdenv.mkDerivation rec {
   meta = {
     description = "Netkit TFTP client and server";
     homepage = "ftp://ftp.uk.linux.org/pub/linux/Networking/netkit/";
-    license = "BSD-Original";
+    license = stdenv.lib.licenses.bsdOriginal;
     maintainers = with stdenv.lib.maintainers; [viric];
     platforms = with stdenv.lib.platforms; linux;
   };