Signed-off-by: Nyangfasheng <yangfasheng@live.com>

Update version number to v4.0.1

更正为正确的Doxygen组定义语法

sync smp skeleton

2 RTM_EXPORT(rt_cpus_lock_status_restore)
3 sync ARCH_CPU_STACK_GROWS_UPWARD in _rt_scheduler_stack_check()

Update license for RT-Thread kernel.

[kernel] add RT_USED to INIT_EXPORT, so that the initialization function is not deleted when it is linked.

Remove the restriction of RT_USING_POSIX for waitqueue structure.

1. Remove INIT_FS_EXPORT and change INIT_DEVICE_EXPORT as the first item
in the initalization thread.
2. Move the eth_system_device_init into INIT_PREV_EXPORT item.

1. Add macro check in rtdebug.h;
2. Use RT_USING_POSIX for poll/select, stdin etc.
3. Split dfs_posix.h to dfs_posix.h, dfs_poll.h and dfs_select.h;