Preprocess all binary SDK symbols to add an sdk_ prefix

* This fixes the problem of axTLS symbols hmac_md5/hmac_sha1 having same
  name as symbols in libwpa (which have incompatible signatures)

* Also allows for easier identification and piece-by-piece removal of
  binary functions.

* Some libc symbols are not renamed, list is in lib/symbols_norename.txt

lwip/esp_interface.c

@@ -47,7 +47,7 @@
 #include "netif/etharp.h"
 
 /* declared in libnet80211.a */
-int8_t ieee80211_output_pbuf(struct netif *ifp, struct pbuf* pb);
+int8_t sdk_ieee80211_output_pbuf(struct netif *ifp, struct pbuf* pb);
 
 static err_t
 low_level_output(struct netif *netif, struct pbuf *p)
@@ -55,7 +55,7 @@ low_level_output(struct netif *netif, struct pbuf *p)
   struct pbuf *q;
 
   for(q = p; q != NULL; q = q->next) {
-      ieee80211_output_pbuf(netif, q);
+      sdk_ieee80211_output_pbuf(netif, q);
   }
 
   LINK_STATS_INC(link.xmit);

lwip/include/arch/cc.h

@@ -35,6 +35,14 @@
 /* include ESP SDK prototypes as they're used in some LWIP routines */
 #include "espressif/sdk_prototypes.h"
 
+/* ESP8266 SDK Interface
+
+   The lwip-esp stack is designed to be also compatible with other ESP8266 SDKs,
+   so we can't use our 'sdk_' prefixes there
+*/
+#define system_station_got_ip_set sdk_system_station_got_ip_set
+#define system_pp_recycle_rx_pkt sdk_system_pp_recycle_rx_pkt
+
 /* Include some files for defining library routines */
 #include <stdio.h> /* printf, fflush, FILE */
 #include <stdlib.h> /* abort */

lwip/include/arch/sys_arch.h

@@ -37,6 +37,8 @@
 #include "queue.h"
 #include "semphr.h"
 
+/* MBOX primitives */
+
 #define SYS_MBOX_NULL					( ( xQueueHandle ) NULL )
 #define SYS_SEM_NULL					( ( xSemaphoreHandle ) NULL )
 #define SYS_DEFAULT_THREAD_STACK_DEPTH	configMINIMAL_STACK_SIZE