Merge pull request #16594 from vpisarev:hull_ordering_fix

fixed the ordering of contour convex hull points

* partially fixed the issue #4539

* fixed warnings and test failures

* fixed integer overflow (issue #14521)

* added comment to force buildbot to re-run

* extended the test for the issue 4539. Check the expected behaviour on the original contour as well

* added comment; fixed typo, renamed another variable for a little better clarity

* added yet another part to the test for issue #4539, where we run convexHull and convexityDetects on the original contour, without any manipulations. the rest of the test stays the same

modules/imgproc/misc/java/test/ImgprocTest.java

@@ -427,7 +427,7 @@ public class ImgprocTest extends OpenCVTestCase {
         Imgproc.convexHull(points, hull);
 
         MatOfInt expHull = new MatOfInt(
-                1, 2, 3, 0
+                0, 1, 2, 3
         );
         assertMatEqual(expHull, hull, EPS);
     }