[barcode] EAN128 FNC1 generation in GNU barcode program

[Alessandro Rubini]

Hello.

> The barcode docs state "--the F1-F4 characters are represented by
> the values 193-196 (0xc1-0xc4, 0301-0304). "

You are right. Here I used the C syntax to write numbers, thus "0301"
as octal representation. This is not meant to be the syntax you
use in your shell to represent the values (each shell is different
in this respect, and if you use other means to create the string using
shell syntax would be not useful anyway.

The reply by Franz Zahaurek is correct. I'm adding a note about shell
syntax to prevent similar problems to other users.

/alessandro