(Alpha and I64 only.) The Convert Numeric Text to Binary
    routines return a binary representation of the ASCII text string
    representation of a decimal, hexadecimal, or octal number.

    Format

      LIB$CVT_DTB_64  byte-count ,numeric-string ,result

      LIB$CVT_HTB_64  byte-count ,numeric-string ,result

      LIB$CVT_OTB_64  byte-count ,numeric-string ,result