Upgrade to openiked-2.1

Changes since 1.10:
o Fix bug FreeBSD/229654: properly generate man pages on FreeBSD.
o Fix Issue #14: properly create iked.conf.5
o Support OpenSSL 1.1 and newer.
o Support for OpenSSL 1.0 has been retained with compatibility defines.

PR: 229654
Reviewed by: mat@
Differential Revision: https://reviews.freebsd.org/D18907