more lwIP physical interfaces (#6680)

This commit adds W5500 W5100 and ENC28j60 drivers from @njh with credits
They are available in libraries/
An example is added in W5500 examples directory

plus:
* Extract dhcp server from lwip2 and add it to the core as a class.
  It must always be present, it is linked and can be called by fw on boot.
  So it cannot be stored in a library.
* ethernet: static or dhcp works
* PPPServer: example
* bring WiFi.config() to the lwIP generic interface (argument reorder common function)
* move hostname() from WiFI-STA to generic interface
* remove non readable characters from dhcp-server comments
* dhcp-server: magic_cookie is part of bootp rfc
* fixes from https://github.com/d-a-v/W5500lwIP/issues/17
* enable lwip_hook_dhcp_parse_option()
* +ethernet tcp client example in w5500 library examples

libraries/ESP8266WiFi/src/ESP8266WiFiSTA.cpp

@@ -26,6 +26,7 @@
 #include "ESP8266WiFiGeneric.h"
 #include "ESP8266WiFiSTA.h"
 #include "PolledTimeout.h"
+#include "LwipIntf.h"
 
 #include "c_types.h"
 #include "ets_sys.h"
@@ -281,28 +282,9 @@ bool ESP8266WiFiSTAClass::config(IPAddress local_ip, IPAddress arg1, IPAddress a
       return true;
   }
 
-  //To allow compatibility, check first octet of 3rd arg. If 255, interpret as ESP order, otherwise Arduino order.
-  IPAddress gateway = arg1;
-  IPAddress subnet = arg2;
-  IPAddress dns1 = arg3;
-
-  if(subnet[0] != 255)
-  {
-    //octet is not 255 => interpret as Arduino order
-    gateway = arg2;
-    subnet = arg3[0] == 0 ? IPAddress(255,255,255,0) : arg3; //arg order is arduino and 4th arg not given => assign it arduino default
-    dns1 = arg1;
-  }
-
-  // check whether all is IPv4 (or gateway not set)
-  if (!(local_ip.isV4() && subnet.isV4() && (!gateway.isSet() || gateway.isV4()))) {
+  IPAddress gateway, subnet, dns1;
+  if (!ipAddressReorder(local_ip, arg1, arg2, arg3, gateway, subnet, dns1))
     return false;
-  }
-
-  //ip and gateway must be in the same subnet
-  if((local_ip.v4() & subnet.v4()) != (gateway.v4() & subnet.v4())) {
-    return false;
-  }
 
 #if !CORE_MOCK
   // get current->previous IP address
@@ -522,94 +504,6 @@ IPAddress ESP8266WiFiSTAClass::dnsIP(uint8_t dns_no) {
     return IPAddress(dns_getserver(dns_no));
 }
 
-
-/**
- * Get ESP8266 station DHCP hostname
- * @return hostname
- */
-String ESP8266WiFiSTAClass::hostname(void) {
-    return wifi_station_get_hostname();
-}
-
-/**
- * Set ESP8266 station DHCP hostname
- * @param aHostname max length:24
- * @return ok
- */
-bool ESP8266WiFiSTAClass::hostname(const char* aHostname) {
-  /*
-  vvvv RFC952 vvvv
-  ASSUMPTIONS
-  1. A "name" (Net, Host, Gateway, or Domain name) is a text string up
-   to 24 characters drawn from the alphabet (A-Z), digits (0-9), minus
-   sign (-), and period (.).  Note that periods are only allowed when
-   they serve to delimit components of "domain style names". (See
-   RFC-921, "Domain Name System Implementation Schedule", for
-   background).  No blank or space characters are permitted as part of a
-   name. No distinction is made between upper and lower case.  The first
-   character must be an alpha character.  The last character must not be
-   a minus sign or period.  A host which serves as a GATEWAY should have
-   "-GATEWAY" or "-GW" as part of its name.  Hosts which do not serve as
-   Internet gateways should not use "-GATEWAY" and "-GW" as part of
-   their names. A host which is a TAC should have "-TAC" as the last
-   part of its host name, if it is a DoD host.  Single character names
-   or nicknames are not allowed.
-  ^^^^ RFC952 ^^^^
-
-  - 24 chars max
-  - only a..z A..Z 0..9 '-'
-  - no '-' as last char
-  */
-
-    size_t len = strlen(aHostname);
-
-    if (len == 0 || len > 32) {
-        // nonos-sdk limit is 32
-        // (dhcp hostname option minimum size is ~60)
-        DEBUG_WIFI_GENERIC("WiFi.(set)hostname(): empty or large(>32) name\n");
-        return false;
-    }
-
-    // check RFC compliance
-    bool compliant = (len <= 24);
-    for (size_t i = 0; compliant && i < len; i++)
-        if (!isalnum(aHostname[i]) && aHostname[i] != '-')
-            compliant = false;
-    if (aHostname[len - 1] == '-')
-        compliant = false;
-
-    if (!compliant) {
-        DEBUG_WIFI_GENERIC("hostname '%s' is not compliant with RFC952\n", aHostname);
-    }
-
-    bool ret = wifi_station_set_hostname(aHostname);
-    if (!ret) {
-        DEBUG_WIFI_GENERIC("WiFi.hostname(%s): wifi_station_set_hostname() failed\n", aHostname);
-        return false;
-    }
-
-    // now we should inform dhcp server for this change, using lwip_renew()
-    // looping through all existing interface
-    // harmless for AP, also compatible with ethernet adapters (to come)
-    for (netif* intf = netif_list; intf; intf = intf->next) {
-
-        // unconditionally update all known interfaces
-        intf->hostname = wifi_station_get_hostname();
-
-        if (netif_dhcp_data(intf) != nullptr) {
-            // renew already started DHCP leases
-            err_t lwipret = dhcp_renew(intf);
-            if (lwipret != ERR_OK) {
-                DEBUG_WIFI_GENERIC("WiFi.hostname(%s): lwIP error %d on interface %c%c (index %d)\n",
-                                   intf->hostname, (int)lwipret, intf->name[0], intf->name[1], intf->num);
-                ret = false;
-            }
-        }
-    }
-
-    return ret && compliant;
-}
-
 /**
  * Return Connection status.
  * @return one of the value defined in wl_status_t