Writes a simple data attribute value to an HDF5 file.
Arguments:
loc_id: The group or dataset the attribute should be written to.
fmt: A string describing the format of the datatype, e.g. char, short, ...
name: The name that should be used for the attribute.
ndims: The rank of the data to be written, between 0-4.
dims: The dimensions of the data, a pointer to ndims number of hsize_t values.
buf: The data that should be written.
Returns 0 upon success, otherwise -1.