Fix dn_comp prototype and add stub

This function is used by ping6 from iputils.

include/resolv.h

@@ -133,7 +133,7 @@ int res_querydomain(const char *, const char *, int, int, unsigned char *, int);
 int res_search(const char *, int, int, unsigned char *, int);
 int res_mkquery(int, const char *, int, int, char *, int, struct rrec *, char *, int);
 int res_send(const char *, int, char *, int);
-int dn_comp(unsigned char *, unsigned char *, int, unsigned char **, unsigned char *, unsigned char **);
+int dn_comp(const char *, unsigned char *, int, unsigned char **, unsigned char **);
 int dn_expand(const unsigned char *, const unsigned char *, const unsigned char *, char *, int);
 int dn_skipname(const unsigned char *, const unsigned char *);
 

src/network/dn_comp.c

@@ -0,0 +1,9 @@
+#include <resolv.h>
+#include "libc.h"
+
+int __dn_comp(const char *src, unsigned char *dst, int space, unsigned char **dnptrs, unsigned char **lastdnptr)
+{
+	return -1;
+}
+
+weak_alias(__dn_comp, dn_comp);