Deprecate IPv6 Destination Options Before the Routing Header

This document deprecates IPv6 Destination Options before the Routing header since there are no known deployments or uses for the Destination Options Header placed ahead in precedence of the Routing Header. It also requires that if a Routing header is present in a packet then it must immediately follow the IPv6 header or immediately follow the Hop-by-Hop Options header if an Hop-by-Hop Options header is also present in the packet. These requirements imply that at most one Routing header may be present in a packet.