Implement auto output resampling (if requested)

If there are for example more than one audio outputs and they have
different sample rates or channels and such, this will allow automatic
conversion of that audio to the request formats/channels/rates (but only
if requested).

plugins/obs-ffmpeg/obs-ffmpeg-output.c

@@ -576,7 +576,7 @@ static bool ffmpeg_output_start(void *data)
 
 	struct audio_convert_info aci;
 	aci.samples_per_sec = SPS_TODO;
-	aci.format          = AUDIO_FORMAT_FLOAT;
+	aci.format          = AUDIO_FORMAT_FLOAT_PLANAR;
 	aci.speakers        = SPEAKERS_STEREO;
 
 	struct video_convert_info vci;