Acknowledge that SSLv3 is also widely considered to be insecure.
Also, provide references for people who want to know more about why it's
insecure.
.IP "-2, --sslv2"
(SSL) Forces curl to use SSL version 2 when negotiating with a remote SSL
server. Sometimes curl is built without SSLv2 support. SSLv2 is widely
-considered insecure.
+considered insecure (see RFC 6176).
.IP "-3, --sslv3"
(SSL) Forces curl to use SSL version 3 when negotiating with a remote SSL
-server. Sometimes curl is built without SSLv3 support.
+server. Sometimes curl is built without SSLv3 support. SSLv3 is widely
+considered insecure (see RFC 7568).
.IP "-4, --ipv4"
This option tells curl to resolve names to IPv4 addresses only, and not for
example try IPv6.