Add a space in the lvlgen pipeline.

Fixes #42.
Use pkg-config on Linux.

Fixes #13
Remove Item.gotit.

Instead, Item.id==0 denotes a slot in the zone's item array that is
free. This is what zoneadditem assumed anyway.
Don't drop items that can't fit in the zone.

Instead, just pop up a message stating that the area is too cluttered
to drop the item.
Print a message when you try to eat something that's not edible.
Merge pull request #43 from eaburns/dev/pkg-config

Use pkg-config on Linux
Merge pull request #44 from eaburns/dev/pipeline

Add a space in the lvlgen pipeline.
Merge pull request #49 from eaburns/dev/items

Fix item dropping