Version: 25.1 24.5

This is sort of a continuation from Bug #21468 (see
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=21468#46 and the
following).  The overlay with newline approach did indeed turn up some
more problems, so we tried moving to the :overline :underline text
method for Emacs 25, but it turns out this causes Emacs to freeze in
certain circumstances (see
https://github.com/magit/magit/issues/2758#issuecomment-250838301).

There is some sentiment to abandon the horizontal bar effect and settle
for just applying a face, but I think this is a bug in Emacs that should
be fixed regardless.  Or maybe it's just a case of "if it hurts, dont do
it"? (using (window-hscroll) in :align-to specs, that is)

-----------------------

With the code below as overlay-bars.el, run

    emacs -Q overlay-bars.el -l overlay-bars.el

then move point to the end of the long line with all the semicolons, hit
C-SPC, and then C-n.  Emacs gets stuck in an infinite loop that cannot
be interrupted by C-g.