3713 Implement accept4()
3714 Implement pipe2()
3715 Implement dup3()
3716 Implement mkostemp() and mkostemps()
3719 so_socketpair syscall should preserve FD_CLOEXEC flag
Reviewed by: Dan McDonald <danmcd@nexenta.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>
Approved by: Garrett D'Amore <garrett@damore.org>