mechanism.
	
	* oln/debug/print_nbh.hh,
	* oln/debug/iota.hh,
	* oln/core/concept/image_identity.hh,
	* oln/core/gen/op.hh,
	* oln/core/internal/op_image_plus_nbh.hh,
	* oln/core/internal/special_op.hh: New.
	* oln/core/concept/image.hh (fwd_niter, bkd_niter, niter): New.
	* oln/core/concept/neighborhood.hh (category): New.
	(include): Add op_image_plus_nbh.hh.
	(oln_decl_op_plus): New.  Handle "Image + Neighborhood".
	* oln/core/equipment.hh (left, right, oper, tag): New.
	* oln/core/gen/single_value_image.hh: Fix.
	* oln/core/internal/neighborhood_base.hh (category): New.
	(neighborhood_base_): Fix inheritance.
	* oln/core/internal/image_base.hh (image_extension_): New.
	(image_base_): Add dpoint.
	* oln/stc/scoop.hxx (vtypes, super_trait_): Add specialization
	for const types.
	(super_trait_): Handle error when not user-defined.


git-svn-id: https://svn.lrde.epita.fr/svn/oln/trunk@859 4aad255d-cdde-0310-9447-f3009e2ae8c0