* mln/core/dpoints_pixter.hh: Aesthetic changes.
	Add some more documentation.
	(dpoints_fwd_pixter(const Generalized_Pixel<Pref>& const Dps&)):
	Use const_cast instead of legacy casts.
	(mln::dpoints_bkd_pixter<I>): New pixel iterator class.
	* mln/core/pixel.hh (mln::pixel<I>::pixel (I&)): Don't set member
	value_ptr_ to 0, since the super class' ctor already takes care of
	this.
	* mln/core/image1d.hh
	(mln::trait::bkd_qixter< image1d<T>, W >)
	(mln::trait::bkd_qixter< const image1d<T>, W >)
	(mln::trait::fwd_nixter< image1d<T>, W >)
	(mln::trait::fwd_nixter< const image1d<T>, W >)
	(mln::trait::bkd_nixter< image1d<T>, W >)
	(mln::trait::bkd_nixter< const image1d<T>, W >)
	* mln/core/image2d.hh
	(mln::trait::bkd_qixter< image2d<T>, W >)
	(mln::trait::bkd_qixter< const image2d<T>, W >)
	(mln::trait::bkd_nixter< image2d<T>, W >)
	(mln::trait::bkd_nixter< const image2d<T>, W >)
	* mln/core/image3d.hh
	(mln::trait::bkd_qixter< image3d<T>, W >)
	(mln::trait::bkd_qixter< const image3d<T>, W >)
	(mln::trait::fwd_nixter< image3d<T>, W >)
	(mln::trait::fwd_nixter< const image3d<T>, W >)
	(mln::trait::bkd_nixter< image3d<T>, W >)
	(mln::trait::bkd_nixter< const image3d<T>, W >):
	Define these specialisations.
	* mln/core/internal/force_exact.hh (mln::internal::force_exact):
	Use ptrdiff_t instead of int to store the pointer difference.
	Remove dead code.
	* mln/core/macros.hh
	(mln_fwd_qixter_, mln_bkd_qixter_, mln_qixter_)
	(mln_fwd_nixter_, mln_bkd_nixter_, mln_nixter_):
	New macros.
	* tests/dpoints_pixter.cc: Move...
	* tests/core/dpoints_pixter.cc: ...here.
	Exercise mln::dpoints_bkd_pixter as well.
	* tests/Makefile.am (check_PROGRAMS): Remove dpoints_pixter.
	(dpoints_pixter_SOURCES): Move...
	* tests/core/Makefile.am: ...here.
	(check_PROGRAMS): Add dpoints_pixter.


git-svn-id: https://svn.lrde.epita.fr/svn/oln/trunk@1913 4aad255d-cdde-0310-9447-f3009e2ae8c0