the box was bigger than 5px in one direction or another. If it was smaller
than that, the user probably just clicked, rather than drawing a box, because
the MouseToolbar icon is kind of misleading.
git-svn-id: http://svn.openlayers.org/branches/openlayers/2.0@1338 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf