* Fix data race in worker copy
* Fix tile ROI problems

See merge request !98

* Rename deprecated GTest TEST_CASE in TEST_SUITE.
* GTest is set as a conan build depedancy

Use a 2D graphic library for this pupose.

This reverts commit 90ce5c41.

    * tests/CMakeLists.txt
    * tests/graphcut/CMakeLists.txt: Fixed.

	*  mln/transform/chamfer_distance_transform.hpp,
	*  tests/CMakeLists.txt,
	*  tests/transform/CMakeLists.txt,
	*  tests/transform/chamfer_distance_transform.cpp: New.

needed with "make check". Compile other apps with specific target.

	*  CMakeLists.txt,
	*  tests/CMakeLists.txt,
	*  tests/accu/CMakeLists.txt,
	*  tests/colors/CMakeLists.txt,
	*  tests/core/CMakeLists.txt,
	*  tests/draw/CMakeLists.txt,
	*  tests/graph/CMakeLists.txt,
	*  tests/graphcut/CMakeLists.txt,
	*  tests/io/CMakeLists.txt,
	*  tests/labeling/CMakeLists.txt,
	*  tests/morpho/CMakeLists.txt: Fixes.

 	* mln/morpho/saturate.hpp, tests/morpho/saturate.cpp: New.
	* tests/morpho/CMakeLists.txt, tests/CMakeLists.txt: Update
	* img/squares.pgm: New test image.

	* CMakeLists.txt
	* mln/core/image/morphers/extended_by_value_image.hpp
	* mln/core/image/sub_image.hpp
	* mln/core/range/filter.hpp
	* mln/core/range/transform.hpp
	* tests/CMakeLists.txt

	* mln/draw/range/line2d.hpp
	* tests/draw/CMakeLists.txt
	* tests/draw/range/line2d.cpp

	* mln/accu/accumulator.hpp
	* mln/accu/accumulator_base.hpp
	* mln/accu/accumulators/count.hpp
	* mln/accu/accumulators/mean.hpp
	* mln/accu/accumulators/sum.hpp
	* mln/accu/dontcare.hpp
	* mln/core/concept/accumulator.hpp
	* mln/labeling/blobs.hpp
	* tests/CMakeLists.txt
	* tests/accu/CMakeLists.txt
	* tests/accu/count.cpp
	* tests/accu/mean.cpp
	* tests/accu/sum.cpp: New