Created attachment 352994 [details, diff] redland-1.0.16-db6.patch The attached patch fixes that.
+ 04 Aug 2014; Michał Górny <mgorny@gentoo.org> redland-1.0.16.ebuild: + Utilize db-use.eclass to obtain proper include path & library for berkdb. Bugs + #519002 and #476376.