Include Chacha20-Poly1305 into default --data-ciphers when available

Include Chacha20-Poly1305 into default --data-ciphers when available

Most TLS 1.3 libraries inlcude the Chacha20-Poly1305 based cipher suite
beside the AES-GCM based ones int he list of default ciphers suites.
Chacha20-Poly1305 is accepted as good alternative AEAD algorithm to the
AES-GCM algorithm by crypto community.

Follow this and include Chacha20-Poly1305 by default in data-ciphers
when available. This makes picking Chacha20-Poly1305 easier as it only
requires to change server (by changing priority) or client side (removing
AES-GCM from data-ciphers) to change to Chacha20-Poly1305.

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Antonio Quartulli <antonio@openvpn.net>
Message-Id: <20210818213354.687736-2-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg22745.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>