-st-natural-width is useful to request a larger-than-usual width,
add back the max-width removed in commit 702cf52cfc to also request
a smaller-than-usual width as necessary.
Items in the window list should take up a fixed amount of space
unless the list is full and items need to shrink. To achieve this,
replace the max-width with the newly added -st-natural-width.
https://bugzilla.gnome.org/show_bug.cgi?id=695392
This is the most basic version of a workspace switcher, taken from
Frippery Bottom Panel and adapted. It handles clicks and scrolls,
and does not show window thumbnails or shapes.
Note that, differently from the frippery version, it won't change
the workspace layout, and actually assume a linear vertical layout,
which is then shown horizontally. This is to keep compatibility
with the overview, which uses a vertical layout.
https://bugzilla.gnome.org/show_bug.cgi?id=694914
