posix: upgrade libevent from 1.4.7 to 1.4.13

third_party/libevent/min_heap.h

 /*
  * Copyright (c) 2006 Maxim Yegorushkin <maxim.yegorushkin@gmail.com>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 68 matching lines @@
         e->min_heap_idx = -1;
         return e;
     }
     return 0;
 }
 
 int min_heap_erase(min_heap_t* s, struct event* e)
 {
     if(((unsigned int)-1) != e->min_heap_idx)
     {
-        min_heap_shift_down_(s, e->min_heap_idx, s->p[--s->n]);
+        struct event *last = s->p[--s->n];
+        unsigned parent = (e->min_heap_idx - 1) / 2;
+        /* we replace e with the last element in the heap.  We might need to
+           shift it upward if it is less than its parent, or downward if it is
+           greater than one or both its children. Since the children are known
+           to be less than the parent, it can't need to shift both up and
+           down. */
+        if (e->min_heap_idx > 0 && min_heap_elem_greater(s->p[parent], last))
+             min_heap_shift_up_(s, e->min_heap_idx, last);
+        else
+             min_heap_shift_down_(s, e->min_heap_idx, last);
         e->min_heap_idx = -1;
         return 0;
     }
     return -1;
 }
 
 int min_heap_reserve(min_heap_t* s, unsigned n)
 {
     if(s->a < n)
     {
@@ skipping 30 matching lines @@
         if(!(min_heap_elem_greater(e, s->p[min_child])))
             break;
         (s->p[hole_index] = s->p[min_child])->min_heap_idx = hole_index;
         hole_index = min_child;
         min_child = 2 * (hole_index + 1);
         }
     min_heap_shift_up_(s, hole_index,  e);
 }
 
 #endif /* _MIN_HEAP_H_ */