Replace lwip SDK blob with lwip 1.4.1 upstream source

Compiles but won't work yet

lwip/esp_interface.c

@@ -0,0 +1,16 @@
+/* LWIP interface to the ESP SDK MAC layer
+
+   These two symbols are called from libnet80211.a
+*/
+
+/* called from hostap_input... less clear what this is for! */
+void ethernetif_init(void)
+{
+
+}
+
+/* called from ieee80211_deliver_data with new IP frames */
+void ethernetif_input(void)
+{
+
+}