output: removed audio_output.sameInAndOutFormats

Eliminate sameInAndOutFormats and check with audio_format_equals()
each time it this information is needed.  Another 4 bytes saved.

src/output_api.h

@@ -66,7 +66,6 @@ struct audio_output {
 	ConvState convState;
 	char *convBuffer;
 	size_t convBufferLen;
-	int sameInAndOutFormats;
 
 	void *data;
 };