Recursion ugliness with panels_node & views

When adding a (legacy at least) view pane to a panel node, attempts to render the pane on the form (via panels_show_pane()) can result in infinite recursion. It seems that this is largely due to the fact that node_view() is invoked indirectly by the view itself, which runs it back through panels_node...etc. There's a TODO in panels_node.module to this effect.

For the moment, I've just added an extra conditional to panels_show_pane() so that it doesn't render panes for view content types on the content editing form. That's the overall direction we're heading in, anyway.

This is mostly a note to remind me that I need to work on this issue, and at least determine whether or not there's something structurally wrong, or if something could be done structurally better.