Other predicates

It would be useful to have adaptive versions of the following predicates

- `parallelorder`: This predicate is defined by `parallelorder(a, b, p, q) = orient(b - a, q - p, 0)` for points in the plane.
- `acuteangle`: Defined by 

```julia
function acuteangle(p, q, r)
prx, pry = p[1] - r[1], p[2] - r[2]
qrx, qry = q[1] - r[1], q[2] - r[2]
return prx * qrx + pry * qry 
end
```

