Changed the SRU update structures and codecs to reflect the SRU pre 1.0

Changed the SRU update structures and codecs to reflect the SRU pre 1.0
spec, at http://www.loc.gov/standards/sru/record-update/
This has changed the binary layout of the following structs:
Z_SRW_extra_record, Z_SRW_updateRequest, Z_SRW_updateResponse and
bend_update_rr . Patch by Ko van der Sloot.