Bug 5601 Fix processing of DueDate return

Bug 5601 Fix processing of DueDate return

item duedate is not a datetime entity but a string retrieved
direct from the db that only needs restructuring
checkout was doing so but item_info was pretending it was in secs
(actually Item.pm manipulated then overwrote it!!)
assume the date in the db is correct (otherwise madness ensues)
dont try to second guess it
As duedates do not yet include a time element assume end of day
as a safety first

[F. Demians] I confirm Joe Atzberger diagnostic. That's a bug reported by a
library. I've tested Colin Campell solution. It fixes the bug.

Signed-off-by: Frédéric Demians <f.demians@tamil.fr>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>