Move private _PyGen API to internal C API:
* _PyAsyncGenAThrow_Type
* _PyAsyncGenWrappedValue_Type
* _PyCoroWrapper_Type
* _PyGen_FetchStopIterationValue()
* _PyGen_Finalize()
* _PyGen_SetStopIterationValue()
No longer these symbols, except of the ones by the _asyncio shared
extensions.
* Add RETURN_GENERATOR and JUMP_NO_INTERRUPT opcodes.
* Trim frame and generator by word each.
* Minor refactor of frame.c
* Update test.test_sys to account for smaller frames.
* Treat generator functions as normal functions when evaluating and specializing.
* Make generator, coroutine and async gen structs all the same size.
* Store interpreter frame in generator (and coroutine). Reduces the number of allocations neeeded for a generator from two to one.
Move classobject.h, context.h, genobject.h and longintrepr.h header
files from Include/ to Include/cpython/.
Remove redundant "#ifndef Py_LIMITED_API" in context.h.
Remove explicit #include "longintrepr.h" in C files. It's not needed,
Python.h already includes it.