bug#9092: movement cursor in speedbar

[Juanma Barranquero <lekktu@gmail.com>]

emacs -Q -f speedbar

The cursor is at the bottom of the speedbar window.

<up>    ; the cursor moves over the icon in the previous line
<up>
...
<up>    ; the cursor moves over the icons normally
<right> <left>  ; the cursor is again over the icon
<down>   ; now the cursor moves to the space next to the icon.

and from that moment on, even if you move over the icon, the cursor
moves back outside it.

According to Eli, line-move-visual tells vertical-motion which column
the cursor should move to, and that does not work too well with stuff
that isn't text, like an image or a stretch glyph (like the one for
`(space :align-to NN)') display property.

    Juanma