support for subtitles, additional authors, subject.

support for subtitles, additional authors, subject.
This supports is only for MARC <-> OLD-DB link. It worked previously, but values entered as MARC were not reported to OLD-DB, neither values entered as OLD-DB were reported to MARC.
Note that some OLD-DB subs are strange (dummy ?) see OLDmodsubject, OLDmodsubtitle, OLDmodaddiauthor in C4/Biblio.pm
For example it seems impossible to have more that 1 addi author and 1 subtitle. In MARC it's not the case. So, if you enter more than one, I'm afraid only the LAST will be stored.