compat-mode: add --data-cipher-fallback auomatically if requested

compat-mode: add --data-cipher-fallback auomatically if requested

For compatibility with OpenVPN older than 2.4.0, the
'--data-cipher-fallback' argument is automatically added with the same
value as specified by '--cipher'.

This happens only when the user specifies compat-mode with a version
older than 2.4.0.

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Signed-off-by: Antonio Quartulli <a@unstable.cc>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <20210904095629.6273-6-a@unstable.cc>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg22798.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>