Fix canny segment fault (Bug #3978)

Avoid stack overflow based on std::vector cause
std::vector::resize() segmentation fault.

modules/imgproc/src/canny.cpp

@@ -453,7 +453,7 @@ void cv::Canny( InputArray _src, OutputArray _dst,
         if ((stack_top - stack_bottom) + src.cols > maxsize)
         {
             int sz = (int)(stack_top - stack_bottom);
-            maxsize = maxsize * 3/2;
+            maxsize = std::max(maxsize * 3/2, sz + src.cols);
             stack.resize(maxsize);
             stack_bottom = &stack[0];
             stack_top = stack_bottom + sz;