Improving the CentOS7 specific parts
Improving the CentOS7 specific parts

Changing the link  for ffmpeg toward a tutorial with an actual mirror of ffmpeg, and with less hassle.
Adding the deendencies to devtoolset-6 and centos-release-scl to provide a C++11 compatible G++
Green-Star/PeerTube,Green-Star/PeerTube,Green-Star/PeerTube,Chocobozzz/PeerTube,Chocobozzz/PeerTube,Chocobozzz/PeerTube,Chocobozzz/PeerTube,Green-Star/PeerTube