Replace C-style library file handling with RAII approaches

Replace C-style library file handling with RAII approaches

Avoids and fixes leaks of filename strings and file pointers, in
normal and exceptional cases. Also cleans up some possible mismatched
file open and close routines.

Introduced a new header to declare the new smart FILE-pointer type.

Minor fixes to doxygen.

Change-Id: Ia7fcf5c93f2b91a6540cdd3d0e710a787960af98