Performance of find methods, comparison with linear search

[Paul Harris]

> YOU SHOULD comment out the first line of test_kdtree.cpp if you are
> going to run the test with more than 1 probe.
> The first line is #define KDTREE_CHECK_PERFORMANCE_COUNTERS.
> If you run more than 1 probe, it will print out lots of rubbish.  Read
> on for why this line is useful at all...
>

note, i sent a version of the file where that #define was not the
first line.  its the 3rd line or so.  sorry!