Add some missing NULL checks which trigger crashes on low-memory conditions.
Found by Victor Stinner. Will backport when 2.5 branch is unfrozen.
diff --git a/Objects/longobject.c b/Objects/longobject.c
index 6b8d6e4..6d55354 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -1739,6 +1739,8 @@
 	     a->ob_digit[size_a-1] < b->ob_digit[size_b-1])) {
 		/* |a| < |b|. */
 		*pdiv = _PyLong_New(0);
+		if (*pdiv == NULL)
+			return -1;
 		Py_INCREF(a);
 		*prem = (PyLongObject *) a;
 		return 0;
@@ -1749,6 +1751,10 @@
 		if (z == NULL)
 			return -1;
 		*prem = (PyLongObject *) PyLong_FromLong((long)rem);
+		if (*prem == NULL) {
+			Py_DECREF(z);
+			return -1;
+		}
 	}
 	else {
 		z = x_divrem(a, b, prem);
@@ -3204,6 +3210,8 @@
 {
 	if (PyInt_Check(*pw)) {
 		*pw = PyLong_FromLong(PyInt_AS_LONG(*pw));
+		if (*pw == NULL)
+			return -1;
 		Py_INCREF(*pv);
 		return 0;
 	}