Avoid using experimental C++14/17 support in CMake
Avoid using experimental C++14/17 support in CMake

This commit points CMAKE_CXX_STANDARD to the latest non-experimental standard.

CMake announces C++14 and C++17 support even if the
compiler supports it only experimentally (c++1y and c++1z).
It breaks cmake standard detection and requires workarounds
for old compilers.

tesseract-ocr/tesseract,UB-Mannheim/tesseract,stweil/tesseract,amitdo/tesseract,UB-Mannheim/tesseract,amitdo/tesseract,amitdo/tesseract,tesseract-ocr/tesseract,stweil/tesseract,stweil/tesseract,amitdo/tesseract,stweil/tesseract,amitdo/tesseract,stweil/tesseract,UB-Mannheim/tesseract,tesseract-ocr/tesseract,UB-Mannheim/tesseract,tesseract-ocr/tesseract,tesseract-ocr/tesseract,UB-Mannheim/tesseract