* Synchronize the code of the rt mart branch to the master branch.
  * TTY device
  * Add lwP code from rt-smart
  * Add vnode in DFS, but DFS will be re-write for rt-smart
  * There are three libcpu for rt-smart:
    * arm/cortex-a, arm/aarch64
    * riscv64
Co-authored-by: NRbb666 <zhangbingru@rt-thread.com>
Co-authored-by: Nzhkag <zhkag@foxmail.com>

* [fix] Fix simulator compilation warnings

* Update bsp/simulator/rtconfig_project.h
Co-authored-by: Man, Jianting (Meco) <920369182@qq.com>

This reverts commit 6a05ddf6.

* implement extension standard C functions

[libc][time] solve the problem which the os tick can be calculated wrongly because the local variable was not initialized.

* [ulog] 解决ulog开启时间戳后与libc time以及rtc驱动相关函数干涉的问题
* ulog：当发生递归输出时，后续递归想要输出的内容可能会因为防范递归的判断而无法输出
因此修改输出规则，在发生递归时，采用简单的，无格式的方式直接输出。这样既保证不会发生递归输出，也可以保证递归输出的部分可以正常输出。
* [ulog] size_t->rt_size_t NULL->RT_NULL

* [add] the function realization of signal for posix.
* [update] the posix support for armclang.
* [add] the new macro "RT_USING_POSIX_TIMER".
* [modify] select "RT_USING_SOFT_TIMER" when use posix'timer.
* [bug] optimize the logic for the "time_xxx" functions.
* [modify] use "RT_USING_POSIX_TIMER" to protect the macro definition.
* [modify] error code when except happened.
* [delete] the "environ" is useless at this time.

* [posix] POSIX standard implementation for PSE51

- add some posix's interfaces that we haven't before.
- these PR have passed the interface definition test across gcc platfrom;
- have tested base on qemu-a9 and stm32h750-art-pi.

* [newlib] only enable POSIX.1-1990

* update projects

[DeviceDriver][RTC] Remove RT_DEVICE_CTRL_RTC_GET_TIME_US and RT_DEVICE_CTRL_RTC_SET_TIME_US. Add RT_DEVICE_CTRL_RTC_GET_TIMEVAL and RT_DEVICE_CTRL_RTC_SET_TIMEVAL. The RT_DEVICE_CTRL_RTC_GET_TIMEVAL cmd can get second time and microsecond time.

在Linux中settimeofday以及gettimeofday函数的时区功能已经被废弃，因此增加注释予以提示。
gettimeofday实现了tz_minuteswest功能，tz_dsttime功能未实现，按废弃处理；
settimeofday时区功能废弃。