Implement dup3 syscall

[robinyuan1002]

I have implement dup3 syscall, there are three functionality for dup3. First, dup3 have the functionality of dup2. Second, dup3 support O_CLOEXEC which is close newfd when it exec. Third, dup3 return error EINVAL if oldfd equal to newfd. Since there are issue with exec syscall right now I can only test the first and third functionality. The second functionality should work by logic but I need to wait for exec syscall.

[Yaxuan-w]

Need to add test case

[Yaxuan-w]

We'd better to include test files at this point even things like exec would block testing.. This could help us test when other things has been fixed

[Yaxuan-w]

I've fixed dup2 on #117. I think the implementation of dup3 could be something like:

check if oldfd == newfd

call dup2(oldfd, newfd)

call fdtables::set_cloexec(self.cageid, newfd, flag)