shout: enlarge buffer size to 32 kB

I was having problems with shoutcast stream outputs before applying
the attached patch, which enlarges the shoutcast output
buffer. Ideally, this should be configurable, but this resolves the
issue for my needs.

src/output/shout_plugin.h

@@ -52,7 +52,7 @@ struct shout_encoder_plugin {
 };
 
 struct shout_buffer {
-	unsigned char data[8192];
+	unsigned char data[32768];
 	size_t len;
 };