Add short example of using the new API

pep-0432.txt

@@ -511,6 +511,35 @@ All 4 phases will be used by the standard CPython interpreter and the
 proposed System Python interpreter. Other embedding applications may
 choose to skip the step of executing code in the ``__main__`` module.
 
+An embedding application may still continue to leave the second phase
+entirely under CPython's control by using the existing ``Py_Initialize``
+API. Alternatively, if an embedding application wants greater control
+over CPython's initial state, it will be able to use the new, finer
+grained API, which allows the embedding application greater control
+over the initialization process::
+
+    /* Phase 1: Pre-Initialization */
+    Py_CoreConfig core_config = Py_CoreConfig_INIT;
+    PyObject *full_config = NULL;
+    /* Easily control the core configuration */
+    core_config.ignore_environment = 1; /* Ignore environment variables */
+    core_config.use_hash_seed = 0; /* Full hash randomisation */
+    Py_BeginInitialization(&core_config);
+    /* Phase 2: Initialization */
+    full_config = PyDict_New();
+    /* Can preconfigure settings here - they will then be
+     * used to derive other settings */
+    Py_ReadConfiguration(full_config);
+    /* Can completely override derived settings here */
+    Py_EndInitialization(full_config);
+    /* Phase 3: Pre-Main */
+    Py_DECREF(full_config);
+    /* If an embedding application has no real concept of a main module
+     * it can leave the interpreter in this state indefinitely.
+     * Otherwise, it can launch __main__ via the Py_Run*AsMain functions.
+     */
+
+
 Pre-Initialization Phase
 ------------------------