C++11 compatibility

Dear rioters,

there's a long running PR concerning C++11 compatibility: https://github.com/RIOT-OS/RIOT/pull/193

Recently I had a brief discussion with Martin about this PR and if we want the C++ support inside the RIOT kernel.

Without these changes RIOT still support separately built C++ applications and libraries. However, if we want to use C++ _within_ the kernel itself, we need changes like proposed in this PR.

So what do you think? Is this syntactical overhead tolerable for us?

Cheers, Oleg