NAME
        IDtoStr -- convert a longword identifier to a null-terminated string.
                   (V36)

   SYNOPSIS
        str = IDtoStr(id, buf);
        D0            D0  A0

        strptr idtostr(long, strptr);

   FUNCTION
        Writes the ASCII equivalent of the given longword ID into buf as a
        null-terminated string.

   INPUTS
        id - longword ID.
        buf - character buffer to accept string (at least 5 chars).

   RESULT
        str - the value of 'buf'.