OSSIM: avoid pointless comparison of unsigned values with 0

...ssim/src/ossim/base/ossimAdjustableParameterInterface.cpp

Utilities/otbossim/src/ossim/base/ossimCommon.cpp

Utilities/otbossim/src/ossim/base/ossimConnectableObject.cpp

...s/otbossim/src/ossim/base/ossimMultiResLevelHistogram.cpp

Utilities/otbossim/src/ossim/imaging/ossimBitMaskWriter.cpp

Utilities/otbossim/src/ossim/imaging/ossimTableRemapper.cpp

...s/otbossim/src/ossim/plugin/ossimSharedPluginRegistry.cpp

...ssim/src/ossim/support_data/ossimSpotDimapSupportData.cpp