move __res_msend_rc declaration to lookup.h

unlike the other res/dn functions, this one is tied to struct
resolvconf which is not a public interface, so put it in the private
header for its subsystem.

src/network/lookup.h

@@ -35,6 +35,7 @@ int __lookup_name(struct address buf[static MAXADDRS], char canon[static 256], c
 int __lookup_ipliteral(struct address buf[static 1], const char *name, int family);
 
 int __get_resolv_conf(struct resolvconf *, char *, size_t);
+int __res_msend_rc(int, const unsigned char *const *, const int *, unsigned char *const *, int *, int, const struct resolvconf *);
 
 int __dns_parse(const unsigned char *, int, int (*)(void *, int, const void *, int, const void *), void *);
 

src/network/lookup_name.c

@@ -100,7 +100,6 @@ struct dpc_ctx {
 
 int __dn_expand(const unsigned char *, const unsigned char *, const unsigned char *, char *, int);
 int __res_mkquery(int, const char *, int, int, const unsigned char *, int, const unsigned char*, unsigned char *, int);
-int __res_msend_rc(int, const unsigned char *const *, const int *, unsigned char *const *, int *, int, const struct resolvconf *);
 
 #define RR_A 1
 #define RR_CNAME 5