Undo half of the previous change :-(

Setting interp->builtins to the __builtin__ module instead of to its
dictionary had the unfortunate side effect of always running in
restricted execution mode :-(

I will check in a different way of setting __main__.__builtins__ to
the __builtin__ module later.

Also, there was a typo -- a comment was unfinished, and as a result
some finalizations were not being executed.

In Bart Simpson style,

I Will Not Check In Untested Changes.
I Will Not Check In Untested Changes.
I Will Not Check In Untested Changes.
I Will Not Check In Untested Changes.
I Will Not Check In Untested Changes.
I Will Not Check In Untested Changes.
I Will Not Check In Untested Changes.
I Will Not Check In Untested Changes.
I Will Not Check In Untested Changes.
I Will Not Check In Untested Changes.