filter, map, range, and zip were proxied through polyglot.builtins to
ensure that their `future_builtins` forms were used. In python3 this is
no longer needed and they don't need to be imported at all, from
anywhere. So, don't.
Python2 had old-style classes (no "(object)"), and new style classes (with
"object"). Under Py3 this is a noop, so let's drop it to make the code
a bit shorter.
Now replaced in all dynamically loaded code. Recipes/metadata
sources/etc. In the case of recipes, since they get compiled by calibre
we simply make the unicode/unichr names available, no need for any
changes to the actual recipes themselves.
