That means, it should contain a dependency to at least dev-libs/xmlsec-1.2.15, however as I didn't try to compile with dev-libs/xmlsec-1.2.15, I guess it's best to just let libgeier dep on >=dev-libs/xmlsec-1.2.16 which works for me.
I don't see much point in it, as 1.2.16 is the only version of xmlsec we have in the tree. If you still have 1.2.15, you've probably not done updates to your system for a long time and you should expect problems. But it doesn't hurt either, so done.
