Fix pseudo ret comparison

[stilscher]

As described in #574 it leads to an exception during the updating of ids if a pseudo return node is matched with a normal return node during CFG comparison. The initial test case added by @sim642 actually now worked without any changes, probably because the CFG creation was changed meanwhile to use an existing return node and avoid the creation of pseudo-return nodes when possible.
So I created the test case 02-cfg-comparison/02-added-return-after-exit where the problem was still observable. To fix it, I adjusted the comparison of nodes to only match two return nodes if either both are pseudo-return nodes or both are not. I removed the cfg comparison option from the test's configuration, because with #841 all incremental tests will be tested with both, ast and cfg comparison.

Closes #574