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

@@ -30,6 +30,14 @@ New in spot 2.10.3.dev  (not yet released)
     alphabet, in applications where using atomic propositions is
     inconvenient.
 
+  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)
 
   Bugs fixed:

THANKS

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

python/spot/impl.i

@@ -1022,6 +1022,7 @@ 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(),
@@ -1030,6 +1031,7 @@ 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(),
@@ -1055,6 +1057,7 @@ 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(),
@@ -1063,6 +1066,7 @@ 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(),
@@ -1071,6 +1075,7 @@ 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(),
@@ -1079,6 +1084,7 @@ 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(),
@@ -1087,6 +1093,7 @@ 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(),
@@ -1095,6 +1102,7 @@ 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(),
@@ -1123,6 +1131,7 @@ 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(),