threaded resolver: Use pthread_t * for curl_thread_t

... since pthread_t may be non-scalar and/or may represent a real thread
with scalar 0.

Bug: http://curl.haxx.se/bug/view.cgi?id=1314

lib/curl_threads.c

@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2011, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2013, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -63,32 +63,38 @@ static void *curl_thread_create_thunk(void *arg)
 
 curl_thread_t Curl_thread_create(unsigned int (*func) (void*), void *arg)
 {
-  curl_thread_t t;
+  curl_thread_t t = malloc(sizeof(pthread_t));
   struct curl_actual_call *ac = malloc(sizeof(struct curl_actual_call));
-  if(!ac)
-    return curl_thread_t_null;
+  if(!(ac && t))
+    goto err;
 
   ac->func = func;
   ac->arg = arg;
 
-  if(pthread_create(&t, NULL, curl_thread_create_thunk, ac) != 0) {
-    free(ac);
-    return curl_thread_t_null;
-  }
+  if(pthread_create(t, NULL, curl_thread_create_thunk, ac) != 0)
+    goto err;
 
   return t;
+
+err:
+  free(t);
+  free(ac);
+  return curl_thread_t_null;
 }
 
 void Curl_thread_destroy(curl_thread_t hnd)
 {
-  if(hnd != curl_thread_t_null)
-    pthread_detach(hnd);
+  if(hnd != curl_thread_t_null) {
+    pthread_detach(*hnd);
+    free(hnd);
+  }
 }
 
 int Curl_thread_join(curl_thread_t *hnd)
 {
-  int ret = (pthread_join(*hnd, NULL) == 0);
+  int ret = (pthread_join(**hnd, NULL) == 0);
 
+  free(*hnd);
   *hnd = curl_thread_t_null;
 
   return ret;

lib/curl_threads.h

@@ -26,8 +26,8 @@
 #if defined(USE_THREADS_POSIX)
 #  define CURL_STDCALL
 #  define curl_mutex_t           pthread_mutex_t
-#  define curl_thread_t          pthread_t
-#  define curl_thread_t_null     (pthread_t)0
+#  define curl_thread_t          pthread_t *
+#  define curl_thread_t_null     (pthread_t *)0
 #  define Curl_mutex_init(m)     pthread_mutex_init(m, NULL)
 #  define Curl_mutex_acquire(m)  pthread_mutex_lock(m)
 #  define Curl_mutex_release(m)  pthread_mutex_unlock(m)