viogsf from https://git.lopez-snowhill.net/chris/viogsf
Sync to 6c43a992 (30 January 2018)

Include 2 own fixes about OS builds:
- https://github.com/xbmc/audiodecoder.gsf/commit/cb3df9820214093b3d21f8b200eefe5be75ae09e
- https://github.com/xbmc/audiodecoder.gsf/commit/2ce3b8b5cc38d67a1ee0b8755d53d1904d2babe9

Old source:
- https://github.com/kode54/viogsf