* headers.mk: update dist headers.

	* mln/canvas/morpho/all.hh: remove non existing included headers.

	* mln/morpho/tree/compute_attribute_image.hh,
	* mln/canvas/morpho/attribute_filter.hh: add missing include.

	* tests/core/image/plain.cc
	* mln/level/compare.hh,
	* mln/core/pixter2d.hh: add more preconditions.

	* mln/io/dicom/load.hh: update doc.

	* mln/morpho/essential.hh,
	* mln/morpho/all.hh,
	* mln/morpho/closing/algebraic.hh: revamp.

	* mln/morpho/closing/all.hh,
	* mln/morpho/closing/essential.hh,
	* mln/morpho/opening/all.hh,
	* mln/morpho/opening/essential.hh: new files.

	* tests/unit_test/unit-tests.mk: update test list.

git-svn-id: https://svn.lrde.epita.fr/svn/oln/trunk@3453 4aad255d-cdde-0310-9447-f3009e2ae8c0