[Koha] Which ISBN is searched for by Z39.50 ?

[Giuseppe.Angilella at ct.infn.it]

Hi again,

when I used to have a Z39.50 daemon working under RedHat 9.0 with a 1.x 
version of Koha, I noticed that I could _NOT_ search ISBNs in the format 
978...X.

That is, I had to delete the trailing 978 (for "Bookland") and edit the 
last ("control") digit, from the 13-digits string usually produced by a 
barcode scanner.

E.g., 9780486650159 should be edited to    0486650154.
       ^^^         ^                     ^^^         ^

I think this is a bit unconvenient. Since I am a newbie to Koha, I wonder 
whether this is a feature or a bug: which way should one enter one's 
ISBNs, with or without the trailing 978?

Thanks again.

Giuseppe.