Minecraft wiki entry for Development_versions, associated text: Village structures are no longer restricted by biome boundaries.
Meaning that a village that starts in a valid biome can now spread into an adjacent invalid biome.
Now generate in taigas (but not variants).
They are made with spruce log.
Savanna villages are now made with acacia wood instead of oak.
In savannas, acacia logs replace cobblestone in all structures except churches.
Paths no longer generate below sea level, and in non-desert villages they are made with different material depending on the existing terrain.
If replacing grass blocks, the path is made from grass path blocks.
If replacing water or lava, the path is made from planks.
Otherwise, the path is gravel on top of cobblestone (including bridges across ravines).
Sandstone paths still always generate in desert villages.
They have a 2% chance of being a zombie village, determined by Zombie NBT tag in Village.dat.
All generated villagers are instead zombie villagers.
There are no doors or torches in the village.