strigi fails to compile with ffmpeg installed (Bug #353)

<snip>
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:463:52: error: 'AVFormatContext' has no member named 'title'
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:465:32: error: 'AVFormatContext' has no member named 'author'
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:469:64: error: 'AVFormatContext' has no member named 'author'
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:471:32: error: 'AVFormatContext' has no member named 'copyright'
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:472:56: error: 'AVFormatContext' has no member named 'copyright'
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:474:32: error: 'AVFormatContext' has no member named 'comment'
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:475:54: error: 'AVFormatContext' has no member named 'comment'
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:477:32: error: 'AVFormatContext' has no member named 'album'
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:481:56: error: 'AVFormatContext' has no member named 'album'
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:483:32: error: 'AVFormatContext' has no member named 'genre'
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:484:52: error: 'AVFormatContext' has no member named 'genre'
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:486:11: error: 'AVFormatContext' has no member named 'track'
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:487:45: error: 'AVFormatContext' has no member named 'track'
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:489:11: error: 'AVFormatContext' has no member named 'year'
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:490:47: error: 'AVFormatContext' has no member named 'year'
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:493:3: warning: 'void av_close_input_stream(AVFormatContext*)' is deprecated (d
eclared at /usr/include/libavformat/avformat.h:1695) [-Wdeprecated-declarations]
/usr/src/strigi-0.7.5/libstreamanalyzer/plugins/endplugins/ffmpegendanalyzer.cpp
:493:27: warning: 'void av_close_input_stream(AVFormatContext*)' is deprecated (
declared at /usr/include/libavformat/avformat.h:1695) [-Wdeprecated-declarations
]
make²: * [libstreamanalyzer/plugins/endplugins/CMakeFiles/ffmpeg.dir/ffmpege
ndanalyzer.cpp.o] Error 1
make¹: [libstreamanalyzer/plugins/endplugins/CMakeFiles/ffmpeg.dir/all] Er
ror 2
make: ** [all] Error 2
! Problem Detected !
Creating compile log /var/log/sorcery/compile/strigi-0.7.5.bz2
Creating castfs debug log /var/log/sorcery/compile/strigi-0.7.5.castfs.dbglog.bz
2

Spells that encountered problems:
---------------------------------
strigi (build)

Will commit fix shortly. The solution is to document and disable ffmpeg as an optional dependency.