Rename worked fine for me. Tested with app-admin/collectd-5.2.0.
+*mongo-c-driver-0.7.1 (21 Jan 2013) + + 21 Jan 2013; Ultrabug <ultrabug@gentoo.org> +mongo-c-driver-0.7.1.ebuild: + Version bump fix #449120 + done, thx Johan