bug#25906: 25.1; strange behavior of overlapped mouse-face

[Eli Zaretskii]

> From: ynyaaa@gmail.com
> Date: Wed, 01 Mar 2017 12:44:36 +0900
> 
> 
> Evaluating the form below, then move the mouse cursor on the inserted text.
> When it is on aaa, underline is displayed on aaaBBB as expected.
> When it is on ccc, overline is displayed on BBBccc as expected.
> 
> When it is moved holizontally from aaa to BBB, overline is not displayed.
> When it is moved holizontally from ccc to BBB, underline is not displayed.

I cannot reproduce this on my system.  Here the underline is displayed
no matter how I move the mouse pointer.