* Check for duplicate attribute names / function arguments. `make

check' now succeeds :-)
* An attribute set such as `{ foo = { enable = true; };
  foo.port = 23; }' now parses.  It was previously rejected, but I'm
  too lazy to implement the check.  (The only reason to reject it is
  that the reverse, `{ foo.port = 23; foo = { enable = true; }; }', is
  rejected, which is kind of ugly.)

tests/lang/parse-fail-dup-attrs-5.nix

@@ -1,4 +0,0 @@
-{
-  services.ssh = { enable = true; };
-  services.ssh.port = 23;
-}