COMP: Remove compile warning on cygwin

Source/CTest/Curl/hostip4.c

@@ -161,7 +161,7 @@ Curl_addrinfo *Curl_ip2addr(in_addr_t num, char *hostname, int port)
   h->h_aliases = NULL;
 
   /* Now store the dotted version of the address */
-  snprintf(h->h_name, 16, "%s", hostname);
+  snprintf((char*)(h->h_name), 16, "%s", hostname);
 
   ai = Curl_he2ai(h, port);