[Python-3000] set literals

[Diogo Kollross]

> i had this idea -- since quoted literals can be prefixed by a letter
> that alters their meaning, why not use the same semantics
> with curly braces?

String literals are always strings, no matter what kind of string as
defined by the prefix. On the other hand, dictionaries and sets seems
different enough for me to not see the second as a special case of the
first.

Sets literals are not top on my priority list, anyways... =]

-- 
diogoko