cmake_minimum_required: Tolerate unknown future arguments

When a ...<max> version is given that is larger than the running version of CMake, assume that the project is aware of a newer version of CMake and that any unknown arguments are future arguments. This will allow future versions of CMake to add arguments to the command that projects can use without introducing errors in older versions of CMake (back to 3.12).

Follows up !1864 (merged).