Upgrade to C++17

CMakeLists.txt

source/App/BitstreamExtractorApp/CMakeLists.txt

source/App/DecoderAnalyserApp/CMakeLists.txt

source/App/DecoderApp/CMakeLists.txt

source/App/EncoderApp/CMakeLists.txt

source/App/EncoderApp/EncAppCfg.cpp

source/App/Parcat/CMakeLists.txt

source/App/Parcat/parcat.cpp

source/App/SEIRemovalApp/CMakeLists.txt

source/App/StreamMergeApp/CMakeLists.txt

source/Lib/CommonAnalyserLib/CMakeLists.txt

source/Lib/CommonLib/Buffer.h

source/Lib/CommonLib/CMakeLists.txt

source/Lib/CommonLib/ContextModelling.cpp

source/Lib/CommonLib/ContextModelling.h

source/Lib/CommonLib/Contexts.cpp

source/Lib/CommonLib/Contexts.h

source/Lib/CommonLib/Quant.cpp

source/Lib/DecoderAnalyserLib/CMakeLists.txt

source/Lib/DecoderLib/BinDecoder.cpp