Raquet Serialization

The functions asBinary and asHexWKB serialize a raquet value, and raquetFromBinary and raquetFromHexWKB reconstruct it. A tile carries its pixels and its QUADBIN georeferencing in one value, so it round-trips through a portable byte string with no spatial extension involved, and the hexadecimal form lets a tile column round-trip through a text-based COPY. Both output functions accept an optional endianness argument, NDR for little-endian or XDR for big-endian, defaulting to the endianness of the server.