Use a more robust parallelism detection

lib/Slic3r/Layer/BridgeDetector.pm

@@ -247,7 +247,7 @@ sub unsupported_edges {
     
     # split into individual segments and filter out edges parallel to the bridging angle
     @$unsupported = map $_->as_polyline,
-        grep { abs($_->direction - $angle) < epsilon }
+        grep $_->parallel_to($angle),
         map @{$_->lines},
         @$unsupported;