Small clean up to the sound envelope code
Small clean up to the sound envelope code

Made swfdec_audio_event_get_envelop_volume return double not int, so it does
the / 32768 and not the caller

freedesktop-unofficial-mirror/swfdec__swfdec,freedesktop-unofficial-mirror/swfdec__swfdec,mltframework/swfdec,freedesktop-unofficial-mirror/swfdec__swfdec,mltframework/swfdec