raddrinfo.c: suppress a warning

* ext/socket/raddrinfo.c (parse_numeric_port): used only when
  inet_pton() is available.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@50904 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/socket/raddrinfo.c

@@ -154,6 +154,7 @@ struct getaddrinfo_arg
     struct addrinfo **res;
 };
 
+#ifdef HAVE_INET_PTON
 static int
 parse_numeric_port(const char *service, int *portp)
 {
@@ -179,6 +180,7 @@ parse_numeric_port(const char *service, int *portp)
 
     return 1;
 }
+#endif
 
 static void *
 nogvl_getaddrinfo(void *arg)