bug#30544: 26.0.91; ansi-term duplicates 2 line zsh prompts any time windows change (maybe other times)

[Eli Zaretskii]

> From: Aaron Jensen <aaronjensen@gmail.com>
> Date: Wed, 14 Mar 2018 08:59:55 -0700
> Cc: Noam Postavsky <npostavs@gmail.com>
> 
> I saw that you've been doing some term.el work recently. Do you have
> an idea what could be causing this?

See Glenn's message with bisection: as expected, this is due to the
telling the shell to resize its window.