@attention Note that the returned pointer is only valid whilst the result
stream has not been closed.
@param results The result stream.
@param index The field index to get the name of.
@return The name of the field, or NULL on error (errno will be set).
If returned, the name will be a NULL terminated string and may
contain UTF-8 multi-byte characters.
Get the name of a field in a result stream.
@attention Note that the returned pointer is only valid whilst the result stream has not been closed.
@param results The result stream. @param index The field index to get the name of. @return The name of the field, or NULL on error (errno will be set). If returned, the name will be a NULL terminated string and may contain UTF-8 multi-byte characters.