message: Fix -Wshadow in remove_children()
  child variable was shadowing xml_node::child
diff: @@ -6142,13 +6142,13 @@ namespace pugi
  impl::xml_allocator& alloc = impl::get_allocator(_root);
  if (!alloc.reserve()) return false;
  - for (xml_node_struct* child = _root->first_child; child; )
  + for (xml_node_struct* cur = _root->first_child; cur; )
  {
  - xml_node_struct* next = child->next_sibling;
  + xml_node_struct* next = cur->next_sibling;
  - impl::destroy_node(child, alloc);
  + impl::destroy_node(cur, alloc);
  - child = next;
  + cur = next;
  }
  _root->first_child = 0;
  