bug#23897: 25.1.50; Argument at point not being highlighted in eldoc hints

[martin rudalics]

> Here is how to reproduce this bug in the master build in an emacs -Q
> session (and also to verify that this bug is not present in emacs-25 branch
> build):
>
> 1. Launch emacs -Q
> 2. Type "(setq a " in the *scratch* buffer
>
> In *master* build, you see this: http://i.imgur.com/YwBybGU.png
> Note that the SYM argument is not highlighted (made bold).
>
> Whereas this is what I see on the *emacs-25* branch after the same steps
> above: http://i.imgur.com/DveB1le.png
> Note that this time, the correct argument is seen in bold face in the eldoc
> hint.

Confirmed.  Something seems to suppress highlighting in the minibuffer -
displaying eldoc in tooltips works as before.  Could you bisect to find
out what's been causing this?

martin