Ugrade nanoflann could speed up match

[lingerer]

Current nanoflann is 1.5.0,according their release note they improve performance for multi thread and others.
I tried to upgrade 1.5.5 and it works,for small point cloud under thread 2 it reduce speed from 50 ms to 42 ms.So a very easy way is just to upgrade 1.5.5.
From version 1.6, it will compile failed because it require result set must have a sort method.