[crossfade] Add silence detection
Currently it works by specifying a crossfade interval without taking into consideration the sound strength at the end of a current song and the beginning of a consequent song. I have quite a lot of songs which have up to 5 seconds of silence at the end of them, others have a considerable amount of silence at the beginning. Other songs have no silence at all, so there's no way I can specify the right interval to crossfade.
The only way to solve this problem is to preread the specified amount of seconds of audio data, calculate sound level and if it falls below a given value, crossfade should be called into action.
It's already implemented by http://www.eisenlohr.org/xmms-crossfade/ - I hope this plugin will be included into the future Audacious releases.