Kill more warnings from the SGI compiler.
Part of SF patch #434992.
diff --git a/Objects/intobject.c b/Objects/intobject.c
index b0ed82a..282da20 100644
--- a/Objects/intobject.c
+++ b/Objects/intobject.c
@@ -645,7 +645,7 @@
 	if (b >= LONG_BIT) {
 		return PyInt_FromLong(0L);
 	}
-	a = (unsigned long)a << b;
+	a = (long)((unsigned long)a << b);
 	return PyInt_FromLong(a);
 }