reachableroots: fix memleak of integer objects at includepath loop

In the first visit loop, val is decref-ed correctly after PySet_Add().
Let's do the same for the includepath loop.

mercurial/parsers.c

@@ -1232,6 +1232,7 b' static PyObject *reachableroots(indexObj'
 						if (val == NULL)
 							goto bail;
 						PySet_Add(reachable, val);
+						Py_DECREF(val);
 					}
 					Py_DECREF(p);
 				}