Make metadata support a compile-time option. Clean up a few definitions.

mdns.h

@@ -1,6 +1,8 @@
 #ifndef _MDNS_H
 #define _MDNS_H
 
+#include "config.h"
+
 extern int mdns_pid;
 
 void mdns_unregister(void);
@@ -15,11 +17,14 @@ typedef struct {
 
 // text and progress only -- picture feed really buggy from iTunes
 
+#ifdef CONFIG_METADATA
+
 #define METADATA_EXPRESSION config.get_coverart ? "md=0,1,2" : "md=0,2"
 
 #define MDNS_RECORD_WITH_METADATA "tp=UDP", "sm=false", "ek=1", "et=0,1", "cn=0,1", "ch=2", METADATA_EXPRESSION , \
                 "ss=16", "sr=44100", "vn=3", "txtvers=1", \
                 config.password ? "pw=true" : "pw=false"
+#endif
 
 #define MDNS_RECORD_WITHOUT_METADATA "tp=UDP", "sm=false", "ek=1", "et=0,1", "cn=0,1", "ch=2", \
                 "ss=16", "sr=44100", "vn=3", "txtvers=1", \