Minecraft wiki entry for Development_versions, associated text: New game rules: dodaylightcycle, doentitydrops, dofiretick, domobspawning, domobloot, dotiledrops, doweathercycle, keepinventory and mobgriefing
Changes in world generation. Seeds which contain pre-generated structures such as ocean monuments & igloos may generate those structures in different places now.
CanPlaceOn & CanDestroy are now supported in the /replaceitem and /give commands
/locate command will now find more structures
r= tag in the square brackets of @e[<tag>] no longer works due to a bug