Add functionalities to handle compiler warnings

[drdanz]

It would be good to have a set of functions to enable/disable/consider error specific compiler warnings if available on the compiler, possibly on the target (see also https://foonathan.net/2018/10/cmake-warnings/).

Also since our software often does not even enable basic warnings, it would probably be good to have some function to enable a set of default warnings, in order to improve the overall quality of the code.