Add the beginnings of a peers.exchange test and begin to fix fallout.

src/ssb.tests.h

@@ -53,4 +53,10 @@ void tf_ssb_test_go_ssb_room(const tf_test_options_t* options);
 */
 void tf_ssb_test_encrypt(const tf_test_options_t* options);
 
+/**
+** Test peer exchange.
+** @param options The test options.
+*/
+void tf_ssb_test_peer_exchange(const tf_test_options_t* options);
+
 /** @} */