This is a partial revert of bfe20162, which introduced #5658.
This is only partial right now, because I don't fully understand the fix. That commit removed gap support elsewhere (path manipulator, pencil tool), but I'm just focusing on pen tool right now for quick testing.
What is this gap code designed to do? There aren't any comments in the original code. And the comment removing them says "remove boring GAP hack". @jabiertxof do you remember what this gap code is about?