2013-05-07  Sebastian Huber <sebastian.huber@embedded-brains.de>

        * libc/include/sys/config.h (_REENT_GLOBAL_ATEXIT): Define for
        RTEMS.
        * libc/include/sys/reent.h (_reent): Use _REENT_GLOBAL_ATEXIT.
        (_global_atexit): Declare if _REENT_GLOBAL_ATEXIT is defined.
        * libc/reent/reent.c (_reclaim_reent): Remove atexit cleanup if
        _REENT_GLOBAL_ATEXIT is defined.
        (_wrapup_reent): Remove atexit handling if _REENT_GLOBAL_ATEXIT
        is defined.
        * libc/stdlib/__atexit.c (_global_atexit0): Define if
        _REENT_GLOBAL_ATEXIT is defined.
        * libc/stdlib/__call_atexit.c (_global_atexit): Define if
        _REENT_GLOBAL_ATEXIT is defined.