Add failing test reproducing issue #1015.

There is a race condition when connect and bind on a new inproc
endpoint happen "simultaneously" in threads.  Causes the error:
  Assertion failed: ok (ctx.cpp:474)

This is a backport of libzmq:5cf74db6b
by Joe Eli McIlvain <joe.eli.mac@gmail.com>

tests/test_inproc_connect.cpp

@@ -36,6 +36,40 @@ static void pusher (void *ctx)
     assert (rc == 0);
 }
 
+static void simult_conn (void *payload)
+{
+    // Pull out arguments - context followed by endpoint string
+    void* ctx   = (void*)((void**)payload)[0];
+    char* endpt = (char*)((void**)payload)[1];
+
+    // Connect
+    void *connectSocket = zmq_socket (ctx, ZMQ_SUB);
+    assert (connectSocket);
+    int rc = zmq_connect (connectSocket, endpt);
+    assert (rc == 0);
+
+    // Cleanup
+    rc = zmq_close (connectSocket);
+    assert (rc == 0);
+}
+
+static void simult_bind (void *payload)
+{
+    // Pull out arguments - context followed by endpoint string
+    void* ctx   = (void*)((void**)payload)[0];
+    char* endpt = (char*)((void**)payload)[1];
+
+    // Bind
+    void *bindSocket = zmq_socket (ctx, ZMQ_PUB);
+    assert (bindSocket);
+    int rc = zmq_bind (bindSocket, endpt);
+    assert (rc == 0);
+
+    // Cleanup
+    rc = zmq_close (bindSocket);
+    assert (rc == 0);
+}
+
 void test_bind_before_connect()
 {
     void *ctx = zmq_ctx_new ();
@@ -268,6 +302,42 @@ void test_multiple_threads()
     assert (rc == 0);
 }
 
+void test_simultaneous_connect_bind_threads ()
+{
+    const unsigned int no_of_times = 50;
+    void *ctx = zmq_ctx_new ();
+    assert (ctx);
+
+    void *threads[no_of_times*2];
+    void *thr_args[no_of_times][2];
+    char endpts[no_of_times][20];
+
+    // Set up thread arguments: context followed by endpoint string
+    for (unsigned int i = 0; i < no_of_times; ++i)
+    {
+        thr_args[i][0] = (void*) ctx;
+        thr_args[i][1] = (void*) endpts[i];
+        sprintf (endpts[i], "inproc://foo_%d", i);
+    }
+
+    // Spawn all threads as simultaneously as possible
+    for (unsigned int i = 0; i < no_of_times; ++i)
+    {
+        threads[i*2+0] = zmq_threadstart (&simult_conn, (void*)thr_args[i]);
+        threads[i*2+1] = zmq_threadstart (&simult_bind, (void*)thr_args[i]);
+    }
+
+    // Close all threads
+    for (unsigned int i = 0; i < no_of_times; ++i)
+    {
+        zmq_threadclose (threads[i*2+0]);
+        zmq_threadclose (threads[i*2+1]);
+    }
+
+    int rc = zmq_ctx_term (ctx);
+    assert (rc == 0);
+}
+
 void test_identity()
 {
     //  Create the infrastructure
@@ -350,6 +420,7 @@ int main (void)
     test_connect_before_bind_pub_sub ();
     test_multiple_connects ();
     test_multiple_threads ();
+    test_simultaneous_connect_bind_threads ();
     test_identity ();
     test_connect_only ();