Liquid duplication when LOOKING at buckets

[Coolthulhu]

Now that's an arcane bug. I'm in the process of fixing it, but I feel the need to report it just as a warning for the future and possible amusement. I had to debug to find it.

• Get a bucket with liquid. For example, spawn 2 contained colas, spill one and refill the newly opened can with the other.
• Drop the bucket with liquid on the ground
• Examine the tile with the bucket
• Mark the bucket for pickup
• Escape without picking up anything
• There is now a copy of the liquid beneath your feet

The bug is caused because of how we're calculating volume and weight of items to be picked up: we clone the player, give the clone new items and ask how much does the clone's item weight and occupy volume.
But giving any character a bucket with liquid will spill the liquid. This includes the clone who doesn't really exist and will be deleted as soon as the pickup menu is closed.

So by imagining a character who will pick up an item, we create a real copy of said item's contents.