* mln/accu/count.hh,
	* mln/accu/volume.hh:
	Add more documentation.
	Aesthetic changes.
	(mln::accu::count_<T>::result)
	(mln::accu::volume_<I>::result): 
	Remove useless typedef.
	* mln/accu/volume.hh:
	(mln::accu::volume_<I>::height__): Rename member as...
	(mln::accu::volume_<I>::ref_level__): ...this.
	(mln::accu::volume_<I>::take)
	(mln::accu::volume_<I>::set_value):
	Adjust.
	(mln::accu::volume_<I>::init): Likewise.
	Actually initialize all members.
	(mln::accu::count_adjacent_vertices_<P, V>::set_value): Reset
	member ref_level__ and area__. 
	* mln/accu/count_adjacent_vertices.hh
	(mln::accu::count_adjacent_vertices_<P, V>::set_value): Reset
	member vertices_.


git-svn-id: https://svn.lrde.epita.fr/svn/oln/trunk@1992 4aad255d-cdde-0310-9447-f3009e2ae8c0