Merge pull request #1 from CleverRaven/master

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Merge pull request #2 from CleverRaven/master

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Active mutation changeover

Some mutations seem to work better as active ones.  Let's get things
moving.
Tweaks & bugfix

This teaks a few things, adds a very important TODO (active mutations
are Exploitable without it) and fixes #8959.
Fixes an it's -> its case in Icecoon's Weapon Pack mod.
Added "overlay" functionality for player/NPCs.

New tileset IDs:
- overlay_worn_{ITEM ID}, overlay drawn over the character when the item is worn
- overlay_wielded_{ITEM ID}, overlay drawn over the character when the item is wielded
Removed superfluous null-check for worn items.
Fix draw_entity_with_overlays return type.

Function doesn't return anything.
Carnivore nutrition

KarmaChimera and Grizzlyadamz made a good point on the IRC: tough to get
Healthy food for Carnivores.

This helps take the edge off total vitamin dependence, since obligate
carnivores in the wild seem to live reasonably non-diseased lives.
Replaced item.type->id with item.typeId() in player::get_overlay_ids()
Merge pull request #3 from CleverRaven/master

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Fires generate hot air
fixed scrolling in keybinding window
Sushi!

Soy sauce and horseradish are found with other condiments - fastfood,
dining, and kitchen.
Cookbook is found in homebooks and kitchen groups.
Food is craftable-only until we get a sushi restaurant *HINT* where we
can spawn these things in a special item group.
Tweak.
Tweak.
Book spawn tweak.
Fixes missing flag in bigun.
Hot air created by fire lingers longer, and has more strength levels
When loading active items, increment the active_item_count.