[Bug c++/71753] Clamp function does not work with O3 optimization

[lukasz.spintzyk at displaylink dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71753

--- Comment #6 from Łukasz Spintzyk <lukasz.spintzyk at displaylink dot com> ---
I confirm changing the code to use unsigned int fixed the problem.

Also there is no signed overflow errors. 

Thanks a lot.