Add correct flags for DTLS 1.2, update s_server and s_client to handle
DTLS 1.2 methods.
Currently no support for version negotiation: i.e. if client/server selects
DTLS 1.2 it is that or nothing.
(cherry picked from commit c3b344e36a)
Conflicts:
apps/s_server.c
Use the enc_flags field to determine whether we should use explicit IV,
signature algorithms or SHA256 default PRF instead of hard coding which
versions support each requirement.
(cherry picked from commit cbd64894ec)
Conflicts:
ssl/ssl_locl.h