EndType enum order is wrong

From `clipper.hpp`:
```c++
enum EndType {etClosedPolygon, etClosedLine, etOpenButt, etOpenSquare, etOpenRound};
```

And from `Clipper.jl`:
```julia
@enum EndType EndTypeClosedPolygon = 0 EndTypeClosedLine = 1 EndTypeOpenSquare = 2 EndTypeOpenRound = 3 EndTypeOpenButt = 4
```

(butt, square, round) are cyclically permuted.
