Mark BROKEN everywhere: fails to build

Error log on 9.3:
src/mgui/ffviewer.cpp: In function 'bool SeekSetTime(FFViewer&, double)':
src/mgui/ffviewer.cpp:1123: error: 'struct AVFormatContext' has no member named 'data_offset'
scons: *** [build/src/mgui/ffviewer.o] Error 1

Reported by: pkg-fallout