Warning for Utils::POW()

[afabri]

In a testsuite of CGAL where we call functions from OpenGR we get a warning from the compiler concerning the function POW(). It is a false alert, but it might be an indication that the compiler does not recognize that this can be computed at compile time.

You use it here. If I was you I used a left shift instead. I would also use a left shift for the occurences of std:pow(2,..).