process on fork(2).
It is the supposed behavior stated in the manpage of sigaction(2), and
Solaris, NetBSD and FreeBSD 3-STABLE correctly do so.
The previous fix against libc_r/uthread/uthread_fork.c fixed the
problem only for the programs linked with libc_r, so back it out and
fix fork(2) itself to help those not linked with libc_r as well.
PR: kern/26705
Submitted by: KUROSAWA Takahiro <fwkg7679@mb.infoweb.ne.jp>
Tested by: knu, GOTOU Yuuzou <gotoyuzo@notwork.org>,
and some other people
Not objected by: hackers
MFC in: 3 days
fa8314227c