man page of select(2) should mention pselect(2)

Reviewed by:	bcr (manpages), kib, trasz
Approved by:	kib (mentor)
MFC after:	7 days
Sponsored by:	Mysterious Code Ltd.
Differential Revision:	https://reviews.freebsd.org/D25169

lib/libc/sys/select.2

@@ -28,7 +28,7 @@
 .\"     @(#)select.2	8.2 (Berkeley) 3/25/94
 .\" $FreeBSD$
 .\"
-.Dd November 17, 2002
+.Dd June 25, 2020
 .Dt SELECT 2
 .Os
 .Sh NAME
@@ -172,6 +172,7 @@ was invalid.
 .Xr gettimeofday 2 ,
 .Xr kqueue 2 ,
 .Xr poll 2 ,
+.Xr pselect 2 ,
 .Xr read 2 ,
 .Xr recv 2 ,
 .Xr send 2 ,