Python stable ABI: Make calls to `tp_free` go through PyType_GetSlot

The Python type struct changes between versions, and thus direct access to
its fields is not allowed in Stable ABI.
The members can, however, be retrieved using `PyType_GetSlot`.

Commit generated with this semantic patch (see https://coccinelle.lip6.fr ):
```
@@
identifier s;
type t;
@@

- Py_TYPE(s)->tp_free((t*) s);
+ Py_TYPE(s)->tp_free(s);

@@
@@

- Py_TYPE(s)->tp_free(s);
+ freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+ free(s);
```

applied using:

    spatch --sp-file patch.cocci --dir python/ --in-place

python/header-py.c

@@ -327,7 +327,8 @@ static PyObject *hdr_new(PyTypeObject *subtype, PyObject *args, PyObject *kwds)
 static void hdr_dealloc(hdrObject * s)
 {
     if (s->h) headerFree(s->h);
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free(s);
 }
 
 static PyObject * hdr_iternext(hdrObject *s)

python/rpmarchive-py.c

@@ -21,7 +21,8 @@ static void rpmarchive_dealloc(rpmarchiveObject * s)
     rpmfilesFree(s->files);
     rpmfiArchiveClose(s->archive);
     rpmfiFree(s->archive);
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free(s);
 }
 
 static PyObject *rpmarchive_error(int rc)

python/rpmds-py.c

@@ -225,7 +225,8 @@ static void
 rpmds_dealloc(rpmdsObject * s)
 {
     s->ds = rpmdsFree(s->ds);
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free(s);
 }
 
 static Py_ssize_t rpmds_length(rpmdsObject * s)

python/rpmfd-py.c

@@ -140,7 +140,8 @@ static void rpmfd_dealloc(rpmfdObject *s)
     Py_XDECREF(res);
     free(s->mode);
     free(s->flags);
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free(s);
 }
 
 static PyObject *rpmfd_fileno(rpmfdObject *s)

python/rpmfiles-py.c

@@ -20,7 +20,8 @@ struct rpmfileObject_s {
 static void rpmfile_dealloc(rpmfileObject * s)
 {
     s->files = rpmfilesFree(s->files);
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free(s);
 }
 
 static char rpmfile_doc[] =
@@ -379,7 +380,8 @@ struct rpmfilesObject_s {
 static void rpmfiles_dealloc(rpmfilesObject * s)
 {
     s->files = rpmfilesFree(s->files);
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free(s);
 }
 
 static PyObject * rpmfiles_new(PyTypeObject * subtype, PyObject *args, PyObject *kwds)

python/rpmii-py.c

@@ -86,7 +86,8 @@ static void rpmii_dealloc(rpmiiObject * s)
     s->ii = rpmdbIndexIteratorFree(s->ii);
     rpmtdFree(s->keytd);
     Py_DECREF(s->ref);
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free(s);
 }
 
 static int rpmii_bool(rpmiiObject *s)

python/rpmkeyring-py.c

@@ -11,7 +11,8 @@ struct rpmPubkeyObject_s {
 static void rpmPubkey_dealloc(rpmPubkeyObject * s)
 {
     s->pubkey = rpmPubkeyFree(s->pubkey);
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free(s);
 }
 
 static PyObject *rpmPubkey_new(PyTypeObject *subtype, 
@@ -108,7 +109,8 @@ struct rpmKeyringObject_s {
 static void rpmKeyring_dealloc(rpmKeyringObject * s)
 {
     rpmKeyringFree(s->keyring);
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free(s);
 }
 
 static PyObject *rpmKeyring_new(PyTypeObject *subtype, 

python/rpmmi-py.c

@@ -129,7 +129,8 @@ static void rpmmi_dealloc(rpmmiObject * s)
 {
     s->mi = rpmdbFreeIterator(s->mi);
     Py_DECREF(s->ref);
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free(s);
 }
 
 static Py_ssize_t rpmmi_length(rpmmiObject * s)

python/rpmps-py.c

@@ -67,7 +67,8 @@ static PyObject *rpmprob_str(rpmProblemObject *s)
 static void rpmprob_dealloc(rpmProblemObject *s)
 {
     s->prob = rpmProblemFree(s->prob);
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free(s);
 }
 
 PyTypeObject rpmProblem_Type = {

python/rpmstrpool-py.c

@@ -13,7 +13,8 @@ static char strpool_doc[] = "";
 static void strpool_dealloc(rpmstrPoolObject *s)
 {
     s->pool = rpmstrPoolFree(s->pool);
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free(s);
 }
 
 static PyObject *strpool_new(PyTypeObject *subtype,

python/rpmts-py.c

@@ -838,7 +838,8 @@ static void rpmts_dealloc(rpmtsObject * s)
     s->ts = rpmtsFree(s->ts);
     Py_XDECREF(s->scriptFd);
     Py_XDECREF(s->keyList);
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free(s);
 }
 
 static PyObject * rpmts_new(PyTypeObject * subtype, PyObject *args, PyObject *kwds)

python/rpmver-py.c

@@ -14,7 +14,8 @@ static char ver_doc[] = "";
 static void ver_dealloc(rpmverObject *s)
 {
     s->ver = rpmverFree(s->ver);
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free(s);
 }
 
 int verFromPyObject(PyObject *o, rpmver *ver)

python/spec-py.c

@@ -144,7 +144,8 @@ spec_dealloc(specObject * s)
     if (s->spec) {
 	s->spec=rpmSpecFree(s->spec);
     }
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    freefunc free = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free(s);
 }
 
 static PyObject * getSection(rpmSpec spec, int section)