Merge branch 'process-wait' into 'userprog-merge'

Fix race-condition in process result (memory leak), fix infinite loop in donors_list

See merge request lab2425_autumn/pintos_22!33

src/threads/synch.c

@@ -341,6 +341,7 @@ lock_release (struct lock *lock)
      released, transfer the remaining orphaned donors to its donor list. */
   if (max_donor != NULL)
     {
+      list_remove (&max_donor->donor_elem);
       while (!list_empty (&orphan_list))
         list_push_back (&max_donor->donors_list, list_pop_front (&orphan_list));
     }