Add modern C++ variant

Author: vadi2

cpp/ql/src/Likely Bugs/Arithmetic/IntMultToLong.cpp

@@ -4,3 +4,5 @@ long j = i * i; //Wrong: due to overflow on the multiplication between ints,
 
 long k = (long) i * i; //Correct: the multiplication is done on longs instead of ints, 
                        //and will not overflow
+
+long k = static_cast<long>(i * i); //Correct: modern C++