Fix PyIter_Check on older Python vers / type##Ptr unused warning

For PyIter_Check, older versions exposed them as either macros (used in
full API), or a function (for use in limited API). A previous change
exposed PyIter_Check to the dynamic build because Python just moved it
to function-only in 3.10 anyway. Because of that, just make sure we
always grab the function in dynamic builds in earlier versions since
that's what Python eventually did anyway.

src/if_py_both.h

@@ -307,7 +307,7 @@ int Vim_PyRun_SimpleString(const char *str)
 
 // Add a static type
 # define PYTYPE_READY(type) \
-    if (PyType_Ready(&(type))) \
+    if (PyType_Ready(type##Ptr)) \
 	return -1;
 
 #endif

src/if_python3.c

@@ -203,7 +203,7 @@ static HINSTANCE hinstPy3 = 0; // Instance of python.dll
 # ifndef PyMapping_Keys
 #  define PyMapping_Keys py3_PyMapping_Keys
 # endif
-# if PY_VERSION_HEX >= 0x030a00b2
+# if PY_VERSION_HEX >= 0x030a0000
 #  define PyIter_Check py3_PyIter_Check
 # endif
 # define PyIter_Next py3_PyIter_Next
@@ -397,7 +397,7 @@ static PyObject* (*py3_PyDict_GetItemString)(PyObject *, const char *);
 static int (*py3_PyDict_Next)(PyObject *, Py_ssize_t *, PyObject **, PyObject **);
 static PyObject* (*py3_PyLong_FromLong)(long);
 static PyObject* (*py3_PyDict_New)(void);
-# if PY_VERSION_HEX >= 0x030a00b2
+# if PY_VERSION_HEX >= 0x030a0000
 static int (*py3_PyIter_Check)(PyObject *o);
 # endif
 static PyObject* (*py3_PyIter_Next)(PyObject *);
@@ -589,7 +589,7 @@ static struct
     {"PyDict_Next", (PYTHON_PROC*)&py3_PyDict_Next},
     {"PyMapping_Check", (PYTHON_PROC*)&py3_PyMapping_Check},
     {"PyMapping_Keys", (PYTHON_PROC*)&py3_PyMapping_Keys},
-# if PY_VERSION_HEX >= 0x030a00b2
+# if PY_VERSION_HEX >= 0x030a0000
     {"PyIter_Check", (PYTHON_PROC*)&py3_PyIter_Check},
 # endif
     {"PyIter_Next", (PYTHON_PROC*)&py3_PyIter_Next},