stubs: don't call DNS_Name2IPAddress handler directly

Instead of calling the handler directly schedule a timeout with zero
delay for resolving to make the function behave similarly to the real
asynchronous resolver. This should prevent problems with code that
inadvertently depends on this behavior and which would break only when
compiled without support for asynchronous resolving.

nameserv_async.h

@@ -34,8 +34,7 @@
 typedef void (*DNS_NameResolveHandler)(DNS_Status status, int n_addrs, IPAddr *ip_addrs, void *anything);
 
 /* Request resolving of a name to IP address. The handler will be
-   called when the result is available, but it may be also called
-   directly from this function call. */
+   called when the result is available. */
 extern void DNS_Name2IPAddressAsync(const char *name, DNS_NameResolveHandler handler, void *anything);
 
 #endif