* headers.mk: remove to_rgb.hh from distribution.

	* mln/convert/all.hh: remove to_rgb.hh.

	* mln/convert/from_to.hxx: add more predeclarations.

	* mln/convert/impl/from_value_to_value.hh: if no value concept is
	caught in the dispatch, try to call a from_to_ overload.

	* mln/fun/v2v/rgb_to_hsl.hh: add new global variables of function
	converting rgb16 to hsl.

	* mln/value/hsl.hh,
	* mln/value/rgb.hh: add new from_to_ overloads.

	* tests/convert/Makefile.am,
	* tests/convert/to_hsl.cc,
	* tests/convert/to_rgb.cc: new tests. Test conversions with rgb<n> and
	hsl<h,s,l> using from_to.

	* mln/convert/to_rgb.hh: remove. Useless since conversions are now done
	thanks to from_to.

	* tests/unit_test/Makefile.am,
	* tests/unit_test/mln_convert_to_rgb.cc: remove unit_test related to
	to_rgb.hh.

	* mln/fun/v2v/rgb_to_hsl.hh: do not include hsl.hh anymore.

git-svn-id: https://svn.lrde.epita.fr/svn/oln/trunk@3180 4aad255d-cdde-0310-9447-f3009e2ae8c0