[kservice] 完善 API 注释

Improve the Kernel comment

[kernel]Normalized kernel API annotation

[libc] fix the conflict warning of read and write functions

[update] src/thread.c function description.

[bsp]add mindmotion MM32F103xx BSP.

[libc标准化] 使用标准poll.h代替dfs_poll.h

[libc标准化] 将dfs_posix.h的函数声明转移到unix标准头文件中

[remove rtlibc]修复缺失的头文件导致的报错

[remove rtlibc] 修复keil编译不过的问题

[serial] 优化RT_USING_POSIX_TERMIOS预编译

[libc] remove rtlibc

[Netif] Fix the eth_tx_msg protection

The ethernetif use semaphore netif->tx_ack to protect the local variable
`struct eth_tx_msg msg` in function `ethernetif_linkoutput`. But the
function could be called in multiple context: LwIP "tcpip" thread, "erx"
thread(on linkup) and any user thread that call `udp_sendto`. So the
global semaphore protection is not sufficient. It could only wakeup the
top priority waiting thread instead of the thread that owns the `msg`
and may result the `msg` next in the mailbox got destructed.

So to use a `rt_completion` within the `struct eth_tx_msg` and
synchronize on that. This could deal the ownership issue in an easy way.

support ch32f10x family, add ch32f103c8-core bsp

serial: add CTS/RTS flowcontrol.