dtls_get_message changes for state machine move

Create a dtls_get_message function similar to the old dtls1_get_message but
in the format required for the new state machine code. The old function will
eventually be deleted in later commits.

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
diff --git a/ssl/ssl_err.c b/ssl/ssl_err.c
index c54ade4..87a31a6 100644
--- a/ssl/ssl_err.c
+++ b/ssl/ssl_err.c
@@ -112,6 +112,8 @@
     {ERR_FUNC(SSL_F_DTLS1_SEND_SERVER_KEY_EXCHANGE),
      "dtls1_send_server_key_exchange"},
     {ERR_FUNC(SSL_F_DTLS1_WRITE_APP_DATA_BYTES), "dtls1_write_app_data_bytes"},
+    {ERR_FUNC(SSL_F_DTLS_GET_REASSEMBLED_MESSAGE),
+     "DTLS_GET_REASSEMBLED_MESSAGE"},
     {ERR_FUNC(SSL_F_READ_STATE_MACHINE), "READ_STATE_MACHINE"},
     {ERR_FUNC(SSL_F_SSL3_ACCEPT), "ssl3_accept"},
     {ERR_FUNC(SSL_F_SSL3_ADD_CERT_TO_BUF), "SSL3_ADD_CERT_TO_BUF"},