Fix #38 by returning the correct type from TimeStamp_hash.

CHANGES.rst

 ``persistent`` Changelog
 ========================
 
+4.2.1 (TBD)
+-----------
+
+- Fix the hashcode of C ``TimeStamp`` objects on 64-bit Python 3 on
+  Windows.
+
 4.2.0 (2016-05-05)
 ------------------
 

persistent/_timestamp.c

@@ -152,7 +152,12 @@ TimeStamp_richcompare(TimeStamp *self, TimeStamp *other, int op)
     return result;
 }
 
+
+#ifdef PY3K
+static Py_hash_t
+#else
 static long
+#endif
 TimeStamp_hash(TimeStamp *self)
 {
     register unsigned char *p = (unsigned char *)self->data;