* thread.h (__reent_t::init_clib): Declare new function.

* thread.cc (__reent_t::init_clib): Define new function.
(pthread::thread_init_wrapper): Use __reent_t::init_clib to init local clib
storage and set std{in,out,err} appropriately.

winsup/cygwin/thread.h

@@ -108,6 +108,7 @@ struct __reent_t
 {
   struct _reent *_clib;
   struct _winsup_t *_winsup;
+  void init_clib (_reent&);
 };
 
 _winsup_t *_reent_winsup ();