Make IO functions return StatusOr

[PragmaTwice]

Before this PR:

int sock_fd = 0;

Status s = Util::SockConnect(this->host_, this->port_, &sock_fd);
if (!s.IsOK()) {
    return Status(Status::NotOK, "connect the server err: " + s.Msg());
}

useInSomeFunction(sock_fd);

After this PR:

int sock_fd = GET_OR_RET(Util::SockConnect(this->host_, this->port_).Prefixed("connect the server err"));

useInSomeFunction(sock_fd);

or even more simple:

useInSomeFunction(GET_OR_RET(Util::SockConnect(this->host_, this->port_).Prefixed("connect the server err")));

[torwig]

LGTM

[PragmaTwice]

Thanks all. Merging...