[merge-r20.1-b] from hotfix 20.1: fix #549, #553 (Closes #553 and #549)

CHANGELOG

Examples/specular/PolarizedNoAnalyzer.py

Sim/Contrib/RoughMultiLayerContribution.cpp

Sim/Scan/IBeamScan.cpp

...nceData/ExamplesMini/scatter2d/CorrelatedRoughness.int.gz

...enceData/ExamplesMini/scatter2d/RectangularGrating.int.gz

Tests/ReferenceData/Suite/MultiLayerWithRoughness.int.gz

Tests/ReferenceData/Suite/OffspecResonator.int.gz

...renceData/Suite/ThickAbsorptiveSampleWithRoughness.int.gz