compactify gtk menus

[phorminx]

I try to avoid wasting precious space on my desktop. Therefore I am a bit annoyed by the default layout of gtk menus that decorates the parent entry of a menu with a bold ">" or "V" to indicate that this item of the menu gives a submenu. For example, the bookmarks toolbar of firefox puts the items rather far apart from each other to accommodate an extra bold "V" for each of them.

How can I suppress that?

Thanks!