* common.mk: New.
	Include it...
	* scribo.mk,
	* tests/tests.mk:
	...here.
	* src/Makefile.am,
	* src/binarization/Makefile.am,
	* src/debug/Makefile.am,
	* src/filter/Makefile.am,
	* src/misc/Makefile.am,
	* src/multi_scale/Makefile.am,
	* src/preprocessing/Makefile.am,
	* src/primitive/extract/Makefile.am,
	* src/primitive/find/Makefile.am,
	* src/primitive/group/Makefile.am,
	* src/table/Makefile.am,
	* src/text/Makefile.am,
	* tests/filter/Makefile.am,
	* tests/preprocessing/Makefile.am,
	* tests/table/Makefile.am:
	Remove (now useless) `*_SOURCES' variables using
	sed -ri '/^(\s|#)*\S+_SOURCES\s*=\s*\S+.cc\s*$/d'.
	* tests/unit_test/build_unit_test.sh: No longer output `*_SOURCES'
	variables.
	* tests/unit_test/unit-tests.mk: Regen.