DNS resolving timeout change to prevent stack overlapping

Real DNS resolving timeout used by lwip library is 14[s] (7[s] for DNS1 + 7[s] for DNS2). Function WiFiGenericClass::hostByName() has timeout set to lower value (only 4[s]), so callback function may be called after this low timeout and it may overlappe stack memory used now by other function.
Fixes espressif#3722

Author: asier70

Diff for: libraries/WiFi/src/WiFiGeneric.cpp

@@ -664,13 +664,13 @@ int WiFiGenericClass::hostByName(const char* aHostname, IPAddress& aResult)
 {
     ip_addr_t addr;
     aResult = static_cast<uint32_t>(0);
-    waitStatusBits(WIFI_DNS_IDLE_BIT, 5000);
-    clearStatusBits(WIFI_DNS_IDLE_BIT);
+    waitStatusBits(WIFI_DNS_IDLE_BIT, 16000);
+    clearStatusBits(WIFI_DNS_IDLE_BIT | WIFI_DNS_DONE_BIT);
     err_t err = dns_gethostbyname(aHostname, &addr, &wifi_dns_found_callback, &aResult);
     if(err == ERR_OK && addr.u_addr.ip4.addr) {
         aResult = addr.u_addr.ip4.addr;
     } else if(err == ERR_INPROGRESS) {
-        waitStatusBits(WIFI_DNS_DONE_BIT, 4000);
+        waitStatusBits(WIFI_DNS_DONE_BIT, 15000);  //real internal timeout in lwip library is 14[s]
         clearStatusBits(WIFI_DNS_DONE_BIT);
     }
     setStatusBits(WIFI_DNS_IDLE_BIT);