shortcuts for defining block-local private names, plays nicely with @foo syntax

[Brendan Eich]

> Brendan Eich <mailto:brendan at mozilla.org>
> January 21, 2012 4:39 PM
>
> Er, const, I hope -- not let. Right?

And _the_real_foo should be expanded:

   {
     private foo;
     ...
   }

desugars to

   {
     const foo = Name.create("foo");
     ...
   }

with Name.create imported appropriately.

/be