Autoconf: add avTranscoder python file

AvTranscoder depends on ffmpeg.
Autoconf: update ffmpeg python file

Check avfilter and swresample libs in ffmpeg.
Autoconf ffmpeg: resample library

Link with avresample or swresample, depending on the ffmpeg headers.
autoconf: rename avTranscoder to avtranscoder

AvTranscoder project creates libraries in lower case (since version
0.3.0).
Merge pull request #13 from tuttleofx/dev_addAvTranscoder

Add avtranscoder