unicode double-width character support

[obfusk]

I recently ran into Unicode history does not work very well in pyrepl in PyPy and investigated it a bit.

I've got a proof of concept patch (based on the vendored version from PyPy) here: https://github.com/obfusk/pyrepl-wide
It doesn't handle wrapped lines and a few other cases (yet), but it does work quite well otherwise.
It seems to work quite well 😄

Based on a quick look at a diff it seems that the PyPy version doesn't differ much (or in ways not relevant to this).
I'd appreciate some input from someone more familiar with the original code.