Revert "Remove heartbeats completely"

Done too soon, this is for future OpenSSL 1.2.0

This reverts commit 6c62f9e1639a7d1a879f363a99882920104dfedb.

Reviewed-by: Rich Salz <rsalz@openssl.org>
diff --git a/ssl/s3_lib.c b/ssl/s3_lib.c
index 8aab778..2439167 100644
--- a/ssl/s3_lib.c
+++ b/ssl/s3_lib.c
@@ -3047,6 +3047,13 @@
         ret = 1;
         break;
 
+#ifndef OPENSSL_NO_HEARTBEATS
+    case SSL_CTRL_DTLS_EXT_SEND_HEARTBEAT:
+    case SSL_CTRL_GET_DTLS_EXT_HEARTBEAT_PENDING:
+    case SSL_CTRL_SET_DTLS_EXT_HEARTBEAT_NO_REQUESTS:
+        break;
+#endif
+
     case SSL_CTRL_CHAIN:
         if (larg)
             return ssl_cert_set1_chain(s, NULL, (STACK_OF(X509) *)parg);