The speed observed on random data set produced by simple_2.cpp is equivalent
to the original recursive version and faster than the version better this commit
- Deprecate the "hierarchy" implementation detail in the package API.
- Introduce a Location_policy parameter instead.
- Add a "Complexity and Performance" section in the user manual.
- Add a benchmark program (dont_submit'ed for now)
Note : merge done by hand as svnmerge.py got too easily confused...