uname.1: Clarify the -r option

It is some times hard to understand the difference between
kernel version and userland version. So clarify the -r option
of uname(1) in terms of a printed kernel version.

While here, add some cross references:

- cross reference freebsd-version(1) in uname(1)
- cross reference freebsd-version(1) and uname(1) in freebsd-update(8)

PR:		265594
Reported by:	rwatson
Reviewed by:	gbe, imp
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D36516

usr.bin/uname/uname.1

@@ -28,7 +28,7 @@
 .\"	@(#)uname.1	8.3 (Berkeley) 4/8/94
 .\" $FreeBSD$
 .\"
-.Dd November 13, 2020
+.Dd September 14, 2022
 .Dt UNAME 1
 .Os
 .Sh NAME
@@ -82,8 +82,10 @@ uses it to set the
 variable.
 .Pc
 .It Fl r
-Write the current release level of the operating system
+Write the current release level of the kernel
 to standard output.
+.Xr freebsd-version 1
+can be used to print the release level of the userland.
 .It Fl s
 Write the name of the operating system implementation to standard output.
 .It Fl U
@@ -138,6 +140,7 @@ and
 would return
 .Va powerpc64 .
 .Sh SEE ALSO
+.Xr freebsd-version 1 ,
 .Xr feature_present 3 ,
 .Xr getosreldate 3 ,
 .Xr sysctl 3 ,

usr.sbin/freebsd-update/freebsd-update.8

@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd April 22, 2022
+.Dd September 10, 2022
 .Dt FREEBSD-UPDATE 8
 .Os
 .Sh NAME
@@ -256,6 +256,8 @@ Default location where
 stores temporary files and downloaded updates.
 .El
 .Sh SEE ALSO
+.Xr freebsd-version 1 ,
+.Xr uname 1 ,
 .Xr freebsd-update.conf 5 ,
 .Xr nextboot 8
 .Sh AUTHORS