Update security/openvpn 2.5. For 2.3 peers, update your configuration,

...see ports/UPDATING or the
ChangeLog: https://github.com/OpenVPN/openvpn/blob/release/2.5/Changes.rst#overview-of-changes-in-25

Avoid LibreSSL (IGNORE_SSL).
INSTALL_DATA -> INSTALL_MAN for documentation.
Rearrange Makefile according to portclippy.