Bug 31143: Fix/identify all cases where '0000-00-00' may still remain in the database

Bug 31143: Fix/identify all cases where '0000-00-00' may still remain in the database

This patch identifies date fields in the database (timestamp, datetime, date) that are 0000-00-00 and sets them to NULL

Test plan -

Examples of setting up some 0000-00-00 date fields:

e.g. Borrowers table
update borrowers set dateexpiry="0000-00-00" where borrowernumber=49;

e.g. Items table
update items set datelastseen="0000-00-00" where itemnumber=12;

To identify the cases:
1) Set up some 0000-00-00 date fields
2) Run the misc/maintenance/search_for_data_inconsistencies.pl script
3) Run fix_invalid_dates.pl -v

To fix the cases:
1) Run fix_invalid_dates.pl -c -v
2) Notice the value has changed from 0000-00-00 to NULL

e.g. Borrowers table
select dateexpiry from borrowers where borrowernumber=49;

e.g. Items table
select datelastseen from items where itemnumber=12;

Signed-off-by: Shi Yao Wang <shi-yao.wang@inlibro.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>