Adding mp3 codec
Adding XDC_USER_PATH to XDC_PATH for mp3 codec support
Adding XDC_USER_PATH to XDC_PATH for mp3 codec support
Adding mp3 encoder and decoder depending on variables that work as enables
Adding --with-mp3encoder and --with-mp3decoder configure params and some logic to improve the way this codecs are handled
Adding define to Cflags in pkgconfig depending if we have the mp3 encoder or decoder