picotcp: enable multithreading. protect bba input queue with mutex.

tentative fix for MINIDUMP-1Y

core/deps/picotcp/include/arch/pico_posix.h

@@ -24,6 +24,8 @@
    #define TIME_PRESCALE
    #define PICO_SUPPORT_THREADING
  */
+#define PICO_SUPPORT_THREADING
+
 #if defined(NDEBUG) && !defined(DEBUGFAST)
 #define dbg(...)
 #else
@@ -127,6 +129,7 @@ static inline uint32_t PICO_TIME_MS(void)
 extern void *pico_mutex_init(void);
 extern void pico_mutex_lock(void *mux);
 extern void pico_mutex_unlock(void *mux);
+extern void pico_mutex_deinit(void *mux);
 
 /* semaphore implementations (only used in wrapper code) */
 extern void *pico_sem_init(void);

core/network/picoppp.cpp

@@ -938,6 +938,7 @@ static void *pico_thread_func(void *)
 			return nullptr;
 		pico_dev->send = &send_eth_frame;
 		pico_dev->proxied = 1;
+		pico_queue_protect(pico_dev->q_in);
 
 		pico_string_to_ipv4("192.168.169.1", &addr);
 		pico_ip4 ipaddr;
@@ -1091,3 +1092,24 @@ void stop_pico()
 	pico_thread_running = false;
 	pico_thread.WaitToEnd();
 }
+
+// picotcp mutex implementation
+extern "C" {
+
+void *pico_mutex_init(void) {
+	return new std::mutex();
+}
+
+void pico_mutex_lock(void *mux) {
+	((std::mutex *)mux)->lock();
+}
+
+void pico_mutex_unlock(void *mux) {
+	((std::mutex *)mux)->unlock();
+}
+
+void pico_mutex_deinit(void *mux) {
+	delete (std::mutex *)mux;
+}
+
+}