Pretty sure you can solve that just by including Engine/EngineTypes.h (and if you get complains about UWorld, add in Engine/World.h).
Also, the Enum changes are deceptively nasty with 4.15. If you were using TEnumAsByte in any files, they’ll need to be removed and you’ll need to update all those enum classes to be simple enums. The problem comes in that previously saved assets don’t seem to work with the new changes, so you may have to resave/reset any enum values that were previously saved to disk.