bpo-45123: PyAiter_Check and PyObject_GetAiter fix & rename. (GH-28194) (GH-28199)

Fix PyAiter_Check to only check for the `__anext__` presense (not for
`__aiter__`). Rename `PyAiter_Check()` to `PyAIter_Check()`,
`PyObject_GetAiter()` -> `PyObject_GetAIter()`.
diff --git a/PC/python3dll.c b/PC/python3dll.c
index ba0a487..08d3c52 100755
--- a/PC/python3dll.c
+++ b/PC/python3dll.c
@@ -90,7 +90,7 @@ EXPORT_FUNC(Py_SetPythonHome)
 EXPORT_FUNC(Py_SetRecursionLimit)
 EXPORT_FUNC(Py_VaBuildValue)
 EXPORT_FUNC(Py_XNewRef)
-EXPORT_FUNC(PyAiter_Check)
+EXPORT_FUNC(PyAIter_Check)
 EXPORT_FUNC(PyArg_Parse)
 EXPORT_FUNC(PyArg_ParseTuple)
 EXPORT_FUNC(PyArg_ParseTupleAndKeywords)
@@ -447,7 +447,7 @@ EXPORT_FUNC(PyObject_GenericGetAttr)
 EXPORT_FUNC(PyObject_GenericGetDict)
 EXPORT_FUNC(PyObject_GenericSetAttr)
 EXPORT_FUNC(PyObject_GenericSetDict)
-EXPORT_FUNC(PyObject_GetAiter)
+EXPORT_FUNC(PyObject_GetAIter)
 EXPORT_FUNC(PyObject_GetAttr)
 EXPORT_FUNC(PyObject_GetAttrString)
 EXPORT_FUNC(PyObject_GetItem)