Explain how stdin/stdout/stderr are connected in term_start():
- On Unix, they default to pty; only "err_cb" switches stderr to a pipe,
which may cause output order differences due to buffering.
- On MS-Windows with ConPTY, they are always pipes and stdout/stderr
share the same pipe, so "err_cb" cannot separate them.
related: #16354
Co-authored-by: Yasuhiro Matsumoto <mattn.jp@gmail.com>
Signed-off-by: Hirohito Higashi <h.east.727@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>