- Add missing username tags

- Remove a contraction

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

@@ -542,13 +542,13 @@ run_rc_command "$1"</programlisting>
 
     <note>
       <para>User crontabs allow individual users to schedule tasks without the 
-        need for root privileges. Commands in a user's crontab run with the 
+        need for <username>root</username> privileges. Commands in a user's crontab run with the 
         permissions of the user who owns the crontab.</para>
 
       <para>The <username>root</username> user can have a user crontab just like
         any other user. This one is different from
         <filename>/etc/crontab</filename> (the system crontab). Because of the
-        system crontab, there's usually no need to create a user crontab
+        system crontab, there is usually no need to create a user crontab
         for <username>root</username>.</para>
     </note>