- Some s/option/literal tags for consistency

- A process state should not considered as an errorname, literal tags is
  maybe a better choice in this case.

en_US.ISO8859-1/books/handbook/config/chapter.sgml

@@ -1966,7 +1966,7 @@ device_probe_and_attach: cbb0 attach returned 12</screen>
     <sect2>
       <title>Network Limits</title>
 
-      <para>The <option>NMBCLUSTERS</option> kernel configuration
+      <para>The <literal>NMBCLUSTERS</literal> kernel configuration
 	option dictates the amount of network Mbufs available to the
 	system.  A heavily-trafficked server with a low number of Mbufs
 	will hinder &os;'s ability.  Each cluster represents
@@ -1988,17 +1988,17 @@ device_probe_and_attach: cbb0 attach returned 12</screen>
 
       <para><varname>kern.ipc.nmbclusters</varname> loader tunable should
         be used to tune this at boot time.  Only older versions of &os;
-        will require you to use the <option>NMBCLUSTERS</option> kernel
+        will require you to use the <literal>NMBCLUSTERS</literal> kernel
         &man.config.8; option.</para>
 
       <para>For busy servers that make extensive use of the
 	&man.sendfile.2; system call, it may be necessary to increase
 	the number of &man.sendfile.2; buffers via the
-	<option>NSFBUFS</option> kernel configuration option or by
+	<literal>NSFBUFS</literal> kernel configuration option or by
 	setting its value in <filename>/boot/loader.conf</filename>
 	(see &man.loader.8; for details).  A common indicator that
 	this parameter needs to be adjusted is when processes are seen
-	in the <errorname>sfbufa</errorname> state.  The sysctl
+	in the <literal>sfbufa</literal> state.  The sysctl
 	variable <varname>kern.ipc.nsfbufs</varname> is a read-only
 	glimpse at the kernel configured variable.  This parameter
 	nominally scales with <varname>kern.maxusers</varname>,