Extended master secret extension support.

Add and retrieve extended master secret extension, setting the flag
SSL_SESS_FLAG_EXTMS appropriately.

Note: this just sets the flag and doesn't include the changes to
master secret generation.
Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>

ssl/ssl_txt.c

diff --git a/ssl/ssl_txt.c b/ssl/ssl_txt.c
index 76a7cce..e5774d2 100644
--- a/ssl/ssl_txt.c
+++ b/ssl/ssl_txt.c
@@ -244,6 +244,10 @@
                    X509_verify_cert_error_string(x->verify_result)) <= 0)
         goto err;
 
+    if (BIO_printf(bp, "    Extended master secret: %s\n",
+                   x->flags & SSL_SESS_FLAG_EXTMS ? "yes" : "no") <= 0)
+        goto err;
+
     return (1);
  err:
     return (0);