Upstream has released updates that appears to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing
CraftBukkit Changes:
43183eab SPIGOT-5399: spawn-npcs ignored during world generation
e9bb2f15 SPIGOT-5403: isSimilar returns true for different skulls
5c9e7236 SPIGOT-5409: Remove unnecessary defaulting in CraftMetaBookSigned
821238b6 SPIGOT-5412: Use SpawnReason.NATURAL for wandering traders and trader llamas
