Dual DTLS version methods.

Add new methods DTLS_*_method() which support both DTLS 1.0 and DTLS 1.2 and
pick the highest version the peer supports during negotiation.

As with SSL/TLS options can change this behaviour specifically
SSL_OP_NO_DTLSv1 and SSL_OP_NO_DTLSv1_2.

ssl/d1_meth.c

diff --git a/ssl/d1_meth.c b/ssl/d1_meth.c
index 64a22d6..ac86dec 100644
--- a/ssl/d1_meth.c
+++ b/ssl/d1_meth.c
@@ -86,3 +86,10 @@
 			dtls1_get_method,
 			DTLSv1_2_enc_data)
 
+IMPLEMENT_dtls1_meth_func(DTLS_ANY_VERSION,
+			DTLS_method,
+			dtls1_accept,
+			dtls1_connect,
+			dtls1_get_method,
+			DTLSv1_2_enc_data)
+