add dependency of relax_coord_bound set in netcdf-c

[wkliao]

This PR checks the setting of option relax_coord_bound in netcdf-c build (netcdf_meta.h) and adjust the testing program nf_test. This fix relies on netcdf-c #1064. It should resolve #86.

The PR also fixes check for whether netcdf-c is built with parallel I/O enabled from netcdf_meta.h.

[wkliao]

The changes in CMakeLists.txt removes the use of netCDF_LIBRARIES and netCDF_INCLUDE_DIR. It now relies on CMAKE_PREFIX_PATH, a generic cmake variable for searching header and library files. Below is the cmake command I used.

cmake ../netcdf-fortran \
    -DCMAKE_PREFIX_PATH="$NETCDF_DIR;$HDF5_DIR;$PNETCDF_DIR" \
    -DNC_EXTRA_DEPS="-lhdf5_hl -lhdf5 -lpnetcdf -lz -lcurl -ldl -lm"