Pull up following revision(s) (requested by riastradh in ticket #658):

share/man/man4/wg.4: revision 1.8
share/man/man4/wg.4: revision 1.9

wg(4): Rework example numbering for clarity and add IPv6.

Let's avoid triggering unease with host number 0.
PR misc/58015

wg(4): Fix IPv6 numbering in example diagram.

This way it matches the configuration suggested below (which avoids
host number zero on the subnet).

PR misc/58015

(martin)