Expose dn_comp and dn_expand to system C code.

This is needed to compile open-source code that wants to
expand/compress domain names itself, such as ping6.

Bug: 9469682
Change-Id: I339c6538936d05c031bc6fb0a8793aaf1429dea4
diff --git a/libc/include/resolv.h b/libc/include/resolv.h
index 7c34012..36b93ee 100644
--- a/libc/include/resolv.h
+++ b/libc/include/resolv.h
@@ -43,12 +43,14 @@
 extern struct __res_state *__res_state(void);
 #define _res (*__res_state())
 
-/* Base-64 functions - because some code expects it there */
+#define b64_ntop __b64_ntop
+#define b64_pton __b64_pton
+extern int b64_ntop(u_char const*, size_t, char*, size_t);
+extern int b64_pton(char const*, u_char*, size_t);
 
-#define b64_ntop        __b64_ntop
-#define b64_pton        __b64_pton
-extern int   b64_ntop(u_char const *, size_t, char *, size_t);
-extern int   b64_pton(char const *, u_char *, size_t);
+#define dn_comp __dn_comp
+extern int dn_comp(const char*, u_char*, int, u_char**, u_char**);
+extern int dn_expand(const u_char*, const u_char*, const u_char*, char*, int);
 
 __END_DECLS
 
diff --git a/libc/private/resolv_private.h b/libc/private/resolv_private.h
index 3b88f49..37764fb 100644
--- a/libc/private/resolv_private.h
+++ b/libc/private/resolv_private.h
@@ -343,7 +343,9 @@
 extern const struct res_sym __p_rcode_syms[];
 #endif /* SHARED_LIBBIND */
 
+#ifndef ANDROID_CHANGES
 #define dn_comp			__dn_comp
+#endif
 #define dn_count_labels		__dn_count_labels
 #define dn_skipname		__dn_skipname
 #define fp_resstat		__fp_resstat
@@ -438,9 +440,6 @@
 const char *	p_option(u_long);
 char *		p_secstodate(u_long);
 int		dn_count_labels(const char *);
-int		dn_comp(const char *, u_char *, int, u_char **, u_char **);
-int		dn_expand(const u_char *, const u_char *, const u_char *,
-			       char *, int);
 u_int		res_randomid(void);
 int		res_nameinquery(const char *, int, int, const u_char *,
 				     const u_char *);