[ubuntu-dev] improve cloud9 c++ auto-completion

[jankeromnes]

@fiji-flo recently emailed me some details about how he improved C++ autocompletion in Cloud9 IDE a few years ago. This could be useful for us:

I dug up my old project to look how I did the autocomplete: https://github.com/fiji-flo/mozdock/blob/master/c9cpp/Dockerfile

It's just using https://github.com/invokr/c9.ide.language.cpp

Worked pretty good back in the days. If I find some time I'll make PR, but please don't wait for it, if you wanna add it yourself (I have some busy holidays coming up).

Thanks Florian! 😄 And happy holidays!