#859 player_pygtk is missing libraries

[Kees Blom]

On Ubuntu 14.04, starting player_pygtk after installing AmbulantPlayer in default
location /usr/local, it crashes with the message:
ImportError: /usr/lib/python2.7/dist-packages/ambulant.so: undefined symbol: _ZN8ambulant3net31get_ffmpeg_audio_decoder_finderEv

A workaround is, to LD_PRELOAD external libraries:
export LD_PRELOAD="/usr/local/lib/libambulant_ffmpeg.so /usr/local/lib/libambulant_gtk.so /usr/local/lib/libambulant_sdl.so"