Consolidate the occurrances of the prime used as the multiplier when hashing
to a single #define instead of having several copies in several files.

This excludes the Modules/ tree (datetime and expat both have a copy
for their own purposes with no need for it to be the same).
diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
index 8aacd12..f6dbc31 100644
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -315,7 +315,7 @@
     register Py_hash_t x, y;
     register Py_ssize_t len = Py_SIZE(v);
     register PyObject **p;
-    Py_hash_t mult = 1000003L;
+    Py_hash_t mult = _PyHASH_MULTIPLIER;
     x = 0x345678L;
     p = v->ob_item;
     while (--len >= 0) {