address a new g++-10 warnings

* spot/twa/twa.hh (set_named_prop): Declare the lambda as noexcept.
* spot/twaalgos/couvreurnew.cc (acss_states): Likewise.

spot/twa/twa.hh

@@ -1120,7 +1120,8 @@ namespace spot
     template<typename T>
     void set_named_prop(std::string s, T* val)
     {
-      set_named_prop(s, val, [](void *p) { delete static_cast<T*>(p); });
+      set_named_prop(s, val,
+                     [](void *p) noexcept { delete static_cast<T*>(p); });
     }
 
     /// \brief Erase a named property

spot/twaalgos/couvreurnew.cc

@@ -360,7 +360,7 @@ namespace spot
       {
         int scc_root = ecs_->root.top().index;
         return T::h_count(ecs_->h,
-            [scc_root](int s) { return s >= scc_root; });
+            [scc_root](int s) noexcept { return s >= scc_root; });
       }
 
       twa_run_ptr