el/dot-emacs.el: Overhaul the point-overlay stuff.

el/dot-emacs.el: Overhaul the point-overlay stuff.

  * Make it capable of displaying a marker in both fringes, and turn
    this on by default.

  * Drop the overlay over the whole line, not just at point.  This
    actually simplifies the positioning code because it doesn't have to
    special-case point at the beginning of the line any more.

  * Lower the overlay priority so that the transient region is still
    visible.

  * Set a face in the overlay so that the line stands out on terminals
    which can't display fringes.

  * Sink the code until after the face machinery, so that we can use it
    for setting the default face.