NetBSD, OpenBSD, and Android's Bionic number the clauses 1 through 3, so follow suit to make comparison easier.
This makes the implementation a bit more consistent with strdup(3), which uses strlen(3).
Copyright attribution is kept the same as in original NetBSD source. Submitted by: Florian Smeets <flo kasimir com> Obtained from: NetBSD MFC after: 2 weeks