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/Python/bltinmodule.c b/Python/bltinmodule.c
index 5e74929..29804f5 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -323,7 +323,7 @@
 		return NULL;
 	if (PyNumber_Coerce(&v, &w) < 0)
 		return NULL;
-	res = Py_BuildValue("(OO)", v, w);
+	res = PyTuple_Pack(2, v, w);
 	Py_DECREF(v);
 	Py_DECREF(w);
 	return res;
@@ -2185,7 +2185,7 @@
 			good = item;
 		}
 		else {
-			PyObject *arg = Py_BuildValue("(O)", item);
+			PyObject *arg = PyTuple_Pack(1, item);
 			if (arg == NULL) {
 				Py_DECREF(item);
 				goto Fail_1;
@@ -2252,7 +2252,7 @@
 			ok = 1;
 		} else {
 			PyObject *arg, *good;
-			arg = Py_BuildValue("(O)", item);
+			arg = PyTuple_Pack(1, item);
 			if (arg == NULL) {
 				Py_DECREF(item);
 				goto Fail_1;
@@ -2346,7 +2346,7 @@
 		if (func == Py_None) {
 			ok = 1;
 		} else {
-			arg = Py_BuildValue("(O)", item);
+			arg = PyTuple_Pack(1, item);
 			if (arg == NULL) {
 				Py_DECREF(item);
 				goto Fail_1;