* mln/topo/is_simple_cell.hh: Make this functor more generic.
	* mln/topo/detach_cell.hh (detach): Turn this function into a
	more generic functor.
	* mln/make/attachment.hh (mln::make::attachment)
	* mln/make/detachment.hh (mln::make::detachment):
	Make these routines more generic.
	* mln/topo/skeleton/breadth_first_thinning.hh
	(mln::topo::skeleton::breadth_first_thinning):
	Adjust.
	* headers.mk: Regen.