Allow faster reuse of socket, to be able to restart WifiServer. Fixes espressif#3960

Author: ahorn42

libraries/WiFi/src/WiFiServer.cpp

@@ -72,6 +72,8 @@ void WiFiServer::begin(uint16_t port){
   sockfd = socket(AF_INET , SOCK_STREAM, 0);
   if (sockfd < 0)
     return;
+  int enable = 1;
+  setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(int));
   server.sin_family = AF_INET;
   server.sin_addr.s_addr = INADDR_ANY;
   server.sin_port = htons(_port);