The language values from the 008 and 041 fields are what's used to determine
the language for the item. It does not differentiate between 041$a (the
current language) and 041$h (original language).
I think it should only search the 041$a because that's the language of the record you're searching for.
Created attachment 3163 [details] [review]
Pushed, please test
This bug is mentioned in:
Bug 5307: Language search fields http://lists.koha-community.org/pipermail/koha-patches/2011-February/013876.html
This does not seem to have been pushed. There is a branch for it at new/bug_5307, but the commit never made it into Master. Changing patch status back to "Signed off."
Merged and pushed, please test