The Convert Hexadecimal Text to Unsigned Integer routine converts
    an ASCII text string representation of an unsigned hexadecimal
    value to an unsigned integer. The integer value can be of
    arbitrary length but is typically a byte, word, longword, or
    quadword. The default size of the result is a longword.

    Format

      OTS$CVT_TZ_L  fixed-or-dynamic-input-string

                    ,varying-output-value [,output-value-size]

                    [,flags-value]