Simplify and speedup uses of Py_BuildValue():

* Py_BuildValue("(OOO)",a,b,c)  -->  PyTuple_Pack(3,a,b,c)
* Py_BuildValue("()",a)         -->  PyTuple_New(0)
* Py_BuildValue("O", a)         -->  Py_INCREF(a)
diff --git a/Modules/symtablemodule.c b/Modules/symtablemodule.c
index f605c22..909a404 100644
--- a/Modules/symtablemodule.c
+++ b/Modules/symtablemodule.c
@@ -31,7 +31,8 @@
 	st = Py_SymtableString(str, filename, start);
 	if (st == NULL)
 		return NULL;
-	t = Py_BuildValue("O", st->st_symbols);
+	t = st->st_symbols;
+	Py_INCREF(t);
 	PyMem_Free((void *)st->st_future);
 	PySymtable_Free(st);
 	return t;