Multiple build warnings in yotta build

[bitsboxscott]

I did the latest steps to get the offline build working in yotta, and it does work, but there are dozens of build warnings, mostly around deprecations. It makes it very challenging to debug your own code changes.

I see multiple warnings like:

CMake Deprecation Warning

and ...

ServiceDiscovery.h:148:77: warning: implicitly-declared 'UUID& UUID::operator=(const UUID&)' is deprecated [-Wdeprecated-copy]

And many more. I'm new to yotta's build system and so far I haven't figured out a way to suppress these warnings. It would be great if the standard instructions led to a warning-less build. But short of that, if anyone has any advice for how I could turn off these warnings, I'd be so grateful.

Thanks! Great library, team. I'm very impressed with this project.

[wdoekes]

@bitsboxscott: the above patches fixes all the gcc warnings I'm encountering.

@"lancaster uni": let me know if I should turn those into PRs here.