interpreter under test is being run in an environment that requires the use of
environment variables such as PYTHONHOME in order to function at all.
Adds a private test.script_helper._interpreter_requires_environment() function
to be used with @unittest.skipIf on stdlib test methods requiring this.
The limit is now 178,956,969 on 64 bit (it is greater on 32 bit because
structures are smaller).
Use int instead of Py_ssize_t to store the number of frames to have smaller
traceback_t objects.