These examples use some datasets that are not included in the source distribution. You can download the datasets from here:

http://people.cs.ubc.ca/~mariusm/uploads/FLANN/datasets/dataset.hdf5
http://people.cs.ubc.ca/~mariusm/uploads/FLANN/datasets/dataset.dat
http://people.cs.ubc.ca/~mariusm/uploads/FLANN/datasets/testset.dat