NetCDF-C++4 API v.4.3.1: unused variable warning

[MetalKnight]

Hello, the latest C++4 APIs v.4.3.1 have the following compiler warning

netcdf4/include/ncGroup.h:18:14: error: ‘netCDF::file_id’ defined but not used [-Werror=unused-variable]
static int file_id;
^

which is preventing compilation with warning treated as errors in programs that compile and link against NetCDF shared objects + include files.

[MetalKnight]

it seems that file_id was added in this commit
ecc2818

but its usage was then removed later on.

furthermore having a static variable in a .h is forcing a definition of the variable in every translation unit that include the .h files, therefore not only the library, but also its clients.