Remove redundant macro and function called `__getreent'

Just rely on the inline version in include/cygwin/config.h

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/cygtls.h

@@ -436,6 +436,4 @@ public:
      _cygtls::call_signal_handler. */
   ~wait_signal_arrived () { _my_tls.unwait_signal_arrived (); }
 };
-
-#define __getreent() (&_my_tls.local_clib)
 /*gentls_offsets*/

winsup/cygwin/thread.cc

@@ -80,13 +80,6 @@ pthread_mutex::no_owner()
     return res;
 }
 
-#undef __getreent
-extern "C" struct _reent *
-__getreent ()
-{
-  return &_my_tls.local_clib;
-}
-
 extern "C" void
 __cygwin_lock_init (_LOCK_T *lock)
 {