Perform build and magnum tuning

Building o//third_party/python now takes 5 seconds on my PC

This change works towards modifying Python to use runtime dispatching
when appropriate. For example, when loading the magnums in the socket
module, it's a good idea to check if the magnum is zero, because that
means the local system platform doesn't support it.

third_party/python/Modules/clinic/_opcode.inc

@@ -0,0 +1,39 @@
+/* clang-format off */
+/*[clinic input]
+preserve
+[clinic start generated code]*/
+
+PyDoc_STRVAR(_opcode_stack_effect__doc__,
+"stack_effect($module, opcode, oparg=None, /)\n"
+"--\n"
+"\n"
+"Compute the stack effect of the opcode.");
+
+#define _OPCODE_STACK_EFFECT_METHODDEF    \
+    {"stack_effect", (PyCFunction)_opcode_stack_effect, METH_VARARGS, _opcode_stack_effect__doc__},
+
+static int
+_opcode_stack_effect_impl(PyObject *module, int opcode, PyObject *oparg);
+
+static PyObject *
+_opcode_stack_effect(PyObject *module, PyObject *args)
+{
+    PyObject *return_value = NULL;
+    int opcode;
+    PyObject *oparg = Py_None;
+    int _return_value;
+
+    if (!PyArg_ParseTuple(args, "i|O:stack_effect",
+        &opcode, &oparg)) {
+        goto exit;
+    }
+    _return_value = _opcode_stack_effect_impl(module, opcode, oparg);
+    if ((_return_value == -1) && PyErr_Occurred()) {
+        goto exit;
+    }
+    return_value = PyLong_FromLong((long)_return_value);
+
+exit:
+    return return_value;
+}
+/*[clinic end generated code: output=4d91c6a765097853 input=a9049054013a1b77]*/