[IronPython] .NET attributes

[Hernan M Foffani]

> Charlie's earlier point about all the different targets is a really good one
> though - worse than even properties are things like arguments, return types,
> etc...  that won't fit in at all w/ decorators.  You could imagine allowing the
> syntax anywhere, but there'd be no way to disambiguate between a return decorator
> and a function decorator in Python.

By using attribute-target specifiers? (type, property, param, field, etc.)

-H.