[gtkmm] TreeView widget sizes

[Carl Nygard <cjnygard fast net>]

I'm trying to size the list entry and column heading buttons smaller
vertically.  I'm using Glade, if that matters.  I can't seem to find any
relevant options to decrease the "whitespace" around the list entries
and column buttons.  I'm aiming for it to be sized similar to the sizes
that Evolution uses.

Any help?

Regards,
Carl