Allow JIT to find _Py_MakeCoro.

Author: markshannon

Include/internal/pycore_ceval.h

@@ -182,7 +182,7 @@ static inline void _Py_LeaveRecursiveCall(void)  {
 
 extern struct _PyInterpreterFrame* _PyEval_GetFrame(void);
 
-extern PyObject* _Py_MakeCoro(PyFunctionObject *func);
+PyAPI_FUNC(PyObject *)_Py_MakeCoro(PyFunctionObject *func);
 
 /* Handle signals, pending calls, GIL drop request
    and asynchronous exception */