Minecraft wiki entry for Development_versions, associated text: Split into 2 different mobs.
New villagers spawn in new villages.
New villager behavior:
Implemented some of the new villager schedule behaviors.
Implemented new villager sleep behaviors.
Villagers may now wander to the village outskirts.
Villagers will attempt to find a door when it rains during the day, but will navigate to their bed at night.
Updated and improved pathfinding.
Villagers now have a visual based trading system, and will hold up the item they wish to trade.
Villagers have new clothing to indicate their level, profession, and biome.
Villagers will now mingle together around gathering sites in the village.
Librarians will inspect bookshelves.
Added Mason and green-robed villagers.
Villagers can change professions depending on the job site blocks available in the village.
Can claim beds and job site blocks.
Villagers can now interact with the corresponding job site block.
Added Mason, green-coated (nitwit), and Unemployed (no-overlay) villager professions.
Old villagers spawn inside igloo basements with textures and behavior prior to Village & Pillage.