simon/os_kernel: An OS kernel for study

simon 29a110d40d fix: fix some problem		8 달 전
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kernel	29a110d40d fix: fix some problem	8 달 전
user	d807627ca3 fixme: 用户进程完善	9 달 전
stdint.h	29a110d40d fix: fix some problem	8 달 전
string.c	4e5987f22e 实现字符串操作函数	10 달 전
string.h	4e5987f22e 实现字符串操作函数	10 달 전