fix bad "licence" names

Mostly what I merged from @lovek323.
Such errors can be easily checked by
  nix-env -f . -qa \* --meta --xml --drv-path --show-trace >/dev/null

pkgs/development/python-modules/pygame/default.nix

@@ -32,6 +32,6 @@ stdenv.mkDerivation {
   meta = {
     description = "Python library for games";
     homepage = "http://www.pygame.org/";
-    licences = "LGPLv2.1+";
+    license = "LGPLv2.1+";
   };
 }