This function adds a new metadata name-value-type tuple to a designated name-value record, where type is hc_timestamp_t. The struct timespec is defined in the POSIX standard:
time_t tv_sec; /* seconds */ long tv_nsec; /* and nanoseconds */
where tv_sec is measured since the UNIX epoch (00:00:00 UTC on January 1, 1970). The maximum value of tv_sec is truncated by three decimal digits owing to database limitations and tv_nsec is truncated to milliseconds. The name-value record automatically expands as needed. The name and value are copied into the structure.