Add target to run self-tests

`make check` is run by the Debian package creator, so it must be a
supported target in the Makefile. For now this is just the same as
`make tests`, but in the future we may/should/must expand this to
also run the tests and figure out if the output is OK (whereas
`make tests` will continue to only compile them)

CMakeLists.txt

@@ -236,6 +236,14 @@ foreach (test_FILE IN LISTS tests_SOURCES)
 	strip_debug_symbols (${test_NAME})
 endforeach (test_FILE)
 
+# ideally this should run the tests, but for now we only test if they
+# compile without errors
+add_custom_target (check
+	DEPENDS tests
+	COMMENT Checking if library is functional
+	VERBATIM
+	)
+
 ### documentation ###
 configure_file (
 	${PROJECT_SOURCE_DIR}/Doxyfile.in