Merge pull request #2525 in HDFFV/hdf5 from ~LRKNOX/hdf5_lrk:develop to develop
* commit '43424a1392b662a29542bb70014c253162ccfe48':
Add missing ')'.
Add C++ warnings treated as error for autotools builds.
Move macro ADD_H5_CFLAGS to cmake_ext_mod/HDFMacros.cmake and remove duplicate versions.
Address PR suggestions and add overlooked GCC compiler version flags.
Don't add general warnings flags for unsupported old versions of gcc and g++ (older than gcc/g++ 4.2). Correct gnu-cxxflags to determine warnings flags to be added based on C++ compiler version instead of C compiler version.