PATCH - use GtkComboBox in the toolbar

Hi,

the attached patch uses GtkComboBox instead of GtkCombo in the
toolbar. The big downside is that GtkComboBox is very opaque and so i
had to deactivate uwog's nice font preview.

It would be very cool if someone could tell me how to use pango markup
in a combo box, or maybe i'll hack the styles combo to use pixbufs to
see if that is feasible. Yet another way would be to intercept the
popup and render a self-coded menu, e.g. for fonts. So the items in
the list could be bigger than the currently selected one in the
non-popped combo.

The rationale behind that is IMHO it's way easier to see what a
style/font looks like /before/ selecting it.

Any advice or comment?

Cheers,
- Rob

PS: no, this won't be committed before we have some kind of preview back.