Add safety cast in queue tutorial code that avoids casting a potentially...

Add safety cast in queue tutorial code that avoids casting a potentially non-pointer-sized "int" to a "void*".

docs/examples/tutorial/clibraries/queue3.pyx

@@ -24,7 +24,7 @@ cdef class Queue:
 
     cpdef append(self, int value):
         if not cqueue.queue_push_tail(self._c_queue,
-                                      <void*> value):
+                                      <void*> <Py_ssize_t> value):
             raise MemoryError()
 
     # The `cpdef` feature is obviously not available for the original "extend()"