Redo the description of kern.quantum vs kern.sched.quantum.

Joel Dahl brought kern.sched.name to my attention after my previous
commit.  Suggest using kern.sched.name instead of "guesswork" for
5.3-RELEASE and later versions, leaving the kern.quantum guessing in
there for a while more (while we support 4.X).

en_US.ISO8859-1/books/faq/book.sgml

@@ -5376,19 +5376,26 @@ device sio5 at isa? port 0x2b8 tty flags 0x501 vector siointr</programlisting>
         </question>
 
         <answer>
-	  <para>Check if you have a sysctl for the round-robin
-	    scheduling quantum.
-	    This is called <literal>kern.quantum</literal> in pre-5.X
-	    versions of &os; and <literal>kern.sched.quantum</literal>
-	    in &os; 5.X or later.
-	    When the sysctl exists, you will see something like this:
-	    <screen>&prompt.user; sysctl <replaceable>kern.sched.quantum</replaceable>
+	  <para>If you are running &os; version 5.2.1 or earlier, check for
+	    the existence of the <literal>kern.quantum</literal> sysctl.
+	    If you have it, you should see something like this:</para>
+
+	  <screen>&prompt.user; sysctl <replaceable>kern.quantum</replaceable>
 kern.sched.quantum: 99960</screen>
-	    When it does not exist, &man.sysctl.8; prints a different
-	    message:
+
+	  <para>If the <literal>kern.quantum</literal> sysctl exists, you are
+	    using the 4BSD scheduler.  If not, you will get an error printed
+	    by &man.sysctl.8; (which you can safely ignore):</para>
+
 	    <screen>&prompt.user; sysctl <replaceable>kern.sched.quantum</replaceable>
 sysctl: unknown oid 'kern.sched.quantum'</screen>
-	    </para>
+
+	  <para>In &os; version 5.3-RELEASE and later, the name of the
+	    scheduler currently being used is directly available as the value
+	    of the <literal>kern.sched.name</literal> sysctl:</para>
+
+	  <screen>&prompt.user; sysctl <replaceable>kern.sched.name</replaceable>
+kern.sched.name: 4BSD</screen>
         </answer>
       </qandaentry>