[DOC] Correct the location of Addrinfo document

The document must be placed immediately before the class definition.
No other statements can be placed in between.

ext/socket/raddrinfo.c

@@ -3030,12 +3030,12 @@ rsock_io_socket_addrinfo(VALUE io, struct sockaddr *addr, socklen_t len)
 void
 rsock_init_addrinfo(void)
 {
+    id_timeout = rb_intern("timeout");
+
     /*
      * The Addrinfo class maps <tt>struct addrinfo</tt> to ruby.  This
      * structure identifies an Internet host and a service.
      */
-    id_timeout = rb_intern("timeout");
-
     rb_cAddrinfo = rb_define_class("Addrinfo", rb_cObject);
     rb_define_alloc_func(rb_cAddrinfo, addrinfo_s_allocate);
     rb_define_method(rb_cAddrinfo, "initialize", addrinfo_initialize, -1);