Unix port: Give threads a name on Linux

May also work on Darwin, but I can't test it :-)

contrib/ports/unix/port/sys_arch.c

@@ -44,6 +44,8 @@
  *    will block until there is more room instead of just
  *    leaking messages.
  */
+#define _GNU_SOURCE /* pull in pthread_setname_np() on Linux */
+
 #include "lwip/debug.h"
 
 #include <string.h>
@@ -190,6 +192,10 @@ sys_thread_new(const char *name, lwip_thread_fn function, void *arg, int stacksi
                         thread_wrapper,
                         thread_data);
 
+#ifdef LWIP_UNIX_LINUX
+  pthread_setname_np(tmp, name);
+#endif
+
   if (0 == code) {
     st = introduce_thread(tmp);
   }