Remove --with-experimental-isolated-subinterpreters configure option
in Python 3.9: the experiment continues in the master branch, but
it's no longer needed in 3.9.
In the experimental isolated subinterpreters build mode, the GIL is
now per-interpreter.
Move gil from _PyRuntimeState.ceval to PyInterpreterState.ceval.
new_interpreter() always get the config from the main interpreter.
Move recursion_limit member from _PyRuntimeState.ceval to
PyInterpreterState.ceval.
* Py_SetRecursionLimit() now only sets _Py_CheckRecursionLimit
of ceval.c if the current Python thread is part of the main
interpreter.
* Inline _Py_MakeEndRecCheck() into _Py_LeaveRecursiveCall().
* Convert _Py_RecursionLimitLowerWaterMark() macro into a static
inline function.
Victor Stinner
Dong-hee Na