select.2: Note that select() and pselect() are not affected by O_NONBLOCK

Reported-by: Robin Kuzmin <kuzmin.robin@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man2/select.2

@@ -398,6 +398,14 @@ Moreover, POSIX requires
 .I fd
 to be a valid file descriptor.
 .PP
+The operation of
+.BR select ()
+and
+.BR pselect ()
+is not affected by the
+.BR O_NONBLOCK
+flag.
+.PP
 On some other UNIX systems,
 .\" Darwin, according to a report by Jeremy Sequoia, relayed by Josh Triplett
 .BR select ()