Fix -Wreorder and simplify AllkNN type.
Fix -Wreorder and simplify AllkNN type.

theranger/mlpack,palashahuja/mlpack,trungda/mlpack,palashahuja/mlpack,datachand/mlpack,datachand/mlpack,thirdwing/mlpack,Azizou/mlpack,ajjl/mlpack,darcyliu/mlpack,darcyliu/mlpack,trungda/mlpack,Azizou/mlpack,chenmoshushi/mlpack,minhpqn/mlpack,chenmoshushi/mlpack,erubboli/mlpack,ersanliqiao/mlpack,datachand/mlpack,trungda/mlpack,ersanliqiao/mlpack,bmswgnp/mlpack,ajjl/mlpack,bmswgnp/mlpack,stereomatchingkiss/mlpack,lezorich/mlpack,lezorich/mlpack,erubboli/mlpack,ersanliqiao/mlpack,thirdwing/mlpack,ajjl/mlpack,BookChan/mlpack,BookChan/mlpack,theranger/mlpack,Azizou/mlpack,minhpqn/mlpack,theranger/mlpack,bmswgnp/mlpack,erubboli/mlpack,minhpqn/mlpack,palashahuja/mlpack,stereomatchingkiss/mlpack,darcyliu/mlpack,ranjan1990/mlpack,lezorich/mlpack,thirdwing/mlpack,BookChan/mlpack,stereomatchingkiss/mlpack,ranjan1990/mlpack,chenmoshushi/mlpack,ranjan1990/mlpack