map::add_item has optional argument to add to OOB coordinates, by calling map::add_item_anywhere(x, y, z, item, maxitems) which adds to any location. (req pr 2176)

requires (and is synced with) https://github.com/CleverRaven/Cataclysm-DDA/pull/2176
required with https://github.com/CleverRaven/Cataclysm-DDA/pull/2312 to close mob corpse blackhole..