Don't use SetPropagatingDict in the built in console

[asmeurer]

Passing a dict subclass to eval is not supported in Python 2. This was causing
weird issues where the C-x would break the UI (I am not clear exactly how it
caused those issues).

The point of SetPropagatingDict is to combine globals and locals into a single
dictionary for things like code.InteractiveConsole and rlcompleter.Completer,
which take a single dictionary, but to allow changes to propagate, so that
assignments in the shell can modify global names. However, this is completely
unnecessary for the built in shell, as we call eval() ourselves, so we can
just pass the exact globals and locals dicts separately.

This fixes #166.

[asmeurer]

I'll also add some comments on SetPropagatingDict so that we can know what it is for in the future.

[inducer]

I'll also add some comments on SetPropagatingDict so that we can know what it is for in the future.

Awesome, thx!

[asmeurer]

Another point of confusion. The usage everywhere is SetPropagatingDict([locals, globals], locals), meaning assignments are supposed to go to locals. But assigning to locals doesn't work. The only reason it works is that at the module level, locals() is globals(). I suppose this is the desired behavior, though, assignments in the shell should work if and only if we are at the module level. It definitely needs some clarification in the code, however.

[inducer]

Thx!