[barcode] Barcode Bugfix

[Robert Pachos]

Hi all,

I have a bugfix to contribute to the GNU Barcode project, but
I am unsure of how to submit the patch and was hoping someone could
provide some direction for me.  I searched for an address for submitting
bugs directly, but was unable to find one.

The fix is to the code93 checksum generation logic, which generates
invalid checksum characters for barcodes longer that 15 digits, and thus
makes them unreadable.

Thanks,

Rob