[3.7] bpo-34247: Fix Python 3.7 initialization (#8659)

* -X dev: it is now possible to override the memory allocator using
  PYTHONMALLOC even if the developer mode is enabled.
* Add _Py_InitializeFromConfig()
* Add _Py_Initialize_ReadEnvVars() to set global configuration
  variables from environment variables
* Fix the code to initialize Python: Py_Initialize() now also reads
  environment variables
* _Py_InitializeCore() can now be called twice: the second call
  only replaces the configuration.
* Write unit tests on Py_Initialize() and the different ways to
  configure Python
* The isolated mode now always sets Py_IgnoreEnvironmentFlag and
  Py_NoUserSiteDirectory to 1.
* pymain_read_conf() now saves/restores the configuration
  if the encoding changed
diff --git a/Include/pystate.h b/Include/pystate.h
index 29d7148..f16ffb8 100644
--- a/Include/pystate.h
+++ b/Include/pystate.h
@@ -79,8 +79,11 @@
 #define _PyCoreConfig_INIT \
     (_PyCoreConfig){ \
         .install_signal_handlers = -1, \
+        .ignore_environment = -1, \
         .use_hash_seed = -1, \
         .coerce_c_locale = -1, \
+        .faulthandler = -1, \
+        .tracemalloc = -1, \
         .utf8_mode = -1, \
         .argc = -1, \
         .nmodule_search_path = -1}