python: fix a memory leak in all added __iter__ methods

Reported by Yechuan Xia

* python/spot/impl.i: Add %newobject to all __iter__ methods.
* NEWS: Mention the list of affected methods.
* THANKS: Update.

NEWS

@@ -1,6 +1,12 @@
 New in spot 2.10.3.dev  (net yet released)
 
-  Nothing yet.
+  Bugs fixed:
+
+  - Fix memory leaks in Python bindings for several iteration objects.
+    This occured while itering on twa_graph.out(), twa_graph.edges(),
+    twa_graph.univ_dests(), kripke_graph.out(), kripke_graph.edges(),
+    mark_t.sets(), scc_info.edges_of(), scc_info.inner_edges_of(), and
+    on an scc_info instance.
 
 New in spot 2.10.3  (2022-01-15)
 

THANKS

@@ -57,5 +57,6 @@ Victor Khomenko
 Vitus Lam
 Yann Thierry-Mieg
 Yannick Molinghen
+Yechuan Xia
 Yong Li
 Yuri Victorovich

python/spot/impl.i

@@ -1012,6 +1012,7 @@ static void* ptr_for_bdddict(PyObject* obj)
 }
 
 %extend spot::internal::state_out<spot::digraph<spot::twa_graph_state, spot::twa_graph_edge_data>> {
+  %newobject __iter__(PyObject **PYTHON_SELF);
   swig::SwigPyIterator* __iter__(PyObject **PYTHON_SELF)
    {
       return swig::make_forward_iterator(self->begin(), self->begin(),
@@ -1020,6 +1021,7 @@ static void* ptr_for_bdddict(PyObject* obj)
 }
 
 %extend spot::internal::state_out<spot::digraph<spot::kripke_graph_state, void>> {
+  %newobject __iter__(PyObject **PYTHON_SELF);
   swig::SwigPyIterator* __iter__(PyObject **PYTHON_SELF)
    {
       return swig::make_forward_iterator(self->begin(), self->begin(),
@@ -1045,6 +1047,7 @@ static void* ptr_for_bdddict(PyObject* obj)
 }
 
 %extend spot::internal::all_trans<spot::digraph<spot::kripke_graph_state, void>> {
+  %newobject __iter__(PyObject **PYTHON_SELF);
   swig::SwigPyIterator* __iter__(PyObject **PYTHON_SELF)
    {
       return swig::make_forward_iterator(self->begin(), self->begin(),
@@ -1053,6 +1056,7 @@ static void* ptr_for_bdddict(PyObject* obj)
 }
 
 %extend spot::internal::all_trans<spot::digraph<spot::twa_graph_state, spot::twa_graph_edge_data>> {
+  %newobject __iter__(PyObject **PYTHON_SELF);
   swig::SwigPyIterator* __iter__(PyObject **PYTHON_SELF)
    {
       return swig::make_forward_iterator(self->begin(), self->begin(),
@@ -1061,6 +1065,7 @@ static void* ptr_for_bdddict(PyObject* obj)
 }
 
 %extend spot::internal::const_universal_dests {
+  %newobject __iter__(PyObject **PYTHON_SELF);
   swig::SwigPyIterator* __iter__(PyObject **PYTHON_SELF)
    {
       return swig::make_forward_iterator_np(self->begin(), self->begin(),
@@ -1069,6 +1074,7 @@ static void* ptr_for_bdddict(PyObject* obj)
 }
 
 %extend spot::internal::mark_container {
+  %newobject __iter__(PyObject **PYTHON_SELF);
   swig::SwigPyIterator* __iter__(PyObject **PYTHON_SELF)
    {
       return swig::make_forward_iterator_np(self->begin(), self->begin(),
@@ -1077,6 +1083,7 @@ static void* ptr_for_bdddict(PyObject* obj)
 }
 
 %extend spot::internal::scc_edges<spot::digraph<spot::twa_graph_state, spot::twa_graph_edge_data> const, spot::internal::keep_all> {
+  %newobject __iter__(PyObject **PYTHON_SELF);
   swig::SwigPyIterator* __iter__(PyObject **PYTHON_SELF)
    {
       return swig::make_forward_iterator(self->begin(), self->begin(),
@@ -1085,6 +1092,7 @@ static void* ptr_for_bdddict(PyObject* obj)
 }
 
 %extend spot::internal::scc_edges<spot::digraph<spot::twa_graph_state, spot::twa_graph_edge_data> const, spot::internal::keep_inner_scc> {
+  %newobject __iter__(PyObject **PYTHON_SELF);
   swig::SwigPyIterator* __iter__(PyObject **PYTHON_SELF)
    {
       return swig::make_forward_iterator(self->begin(), self->begin(),
@@ -1113,6 +1121,7 @@ static void* ptr_for_bdddict(PyObject* obj)
  }
 
 %extend spot::scc_info {
+  %newobject __iter__(PyObject **PYTHON_SELF);
   swig::SwigPyIterator* __iter__(PyObject **PYTHON_SELF)
    {
       return swig::make_forward_iterator(self->begin(), self->begin(),