Update ffmpeg to version 20170731-b664d1f
Update ffmpeg to version 20170731-b664d1f

Congee/scoop,nikolasd/scoop,Cyianor/scoop,kodybrown/scoop,coonce/scoop,rasa/scoop,lukesampson/scoop,yunspace/scoop,reelsense/scoop,berwyn/scoop,vidarkongsli/scoop,toxeus/scoop