Upstream has released updates that appear to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing
Bukkit Changes:
13eb4146 SPIGOT-5217, SPIGOT-6183: Add RespawnReason to PlayerRespawnEvent
CraftBukkit Changes:
5ee3419b7 SPIGOT-5217, SPIGOT-6183: Add RespawnReason to PlayerRespawnEvent
Spigot Changes:
514cf03a Rebuild patches and add RespawnReason.PLUGIN to Player#respawn