/// DTA file format reader.
/// Stata missing value representation.
/// Stata byte value (1-byte signed integer or missing).
/// Stata double value (8-byte IEEE 754 float or missing).
/// Unified error type for Stata value parsing.
/// Stata float value (4-byte IEEE 754 float or missing).
/// Stata int value (2-byte signed integer or missing).
/// Stata long value (4-byte signed integer or missing).
/// Timestamp from a DTA file header.