[SECURITY] Fedora 28 Update: CImg-2.3.6-1.fc28

The CImg Library is an open-source C++ toolkit for image processing. It consists in a single header file ‘CImg.h’ providing a minimal set of C++ classes and methods that can be used in your own sources, to load/save, process and display images. Very portable, efficient and easy to use, it’s a pleasant library for developping image processing algorithms in C++.