Allow the user to have fetch externals build the source packages on unknown distros.
Merge branch 'master' of https://github.com/ms705/firmament into malte
Merge branch 'master' of https://github.com/ms705/firmament into malte
Merge branch 'master' of https://github.com/ms705/firmament into malte
Ensuring Pion is compiled with the C++11 standard. (Ubuntu 14.04 / Arch Linux fix)
Merge pull request #12 from gustafa/malte

Merge @gustafa's fix for pion compilation with C++11 enabled for the main build. (Since we link pion statically, the C++ ABIs must be the same.)