bug#40000: 27.0.60; next-single-char-property-change hangs on bad argument

[Eli Zaretskii]

> From: Federico Tedin <federicotedin@gmail.com>
> Date: Mon, 13 Apr 2020 15:52:17 +0200
> Cc: 40000@debbugs.gnu.org
> 
> I'm attaching a patch which solves the issue. Now, all the
> `next-*-property-change' functions return LIMIT when it has been
> specified and no properties where found up to the buffer's end.

Doesn't that contradict the documentation?  It says:

  If the property is constant all the way to the end of OBJECT, return the
  last valid position in OBJECT.

Your change means this will no longer be true when LIMIT > EOB.

Thanks.