handbook: Improve Firewalls chapter

- Fix some dead links and punctuations
- pfctl_parser.c was moved to a new location since FreeBSD 10
- Fix a few service commands

Issues found when translating this chapter to pt_BR.

Reviewed by:	bcr
Approved by:	doc (bcr)
Differential Revision:	https://reviews.freebsd.org/D18981

en_US.ISO8859-1/books/handbook/firewalls/chapter.xml

@@ -173,8 +173,8 @@
       and do a port number lookup to find the purpose of a particular
       port number.</para>
 
-    <para>Check out this link for port numbers used by Trojans <uri
-	xlink:href="http://www.sans.org/security-resources/idfaq/oddports.php">http://www.sans.org/security-resources/idfaq/oddports.php</uri>.</para>
+    <para>Check out this link for <uri
+	xlink:href="http://web.archive.org/web/20150803024617/http://www.sans.org/security-resources/idfaq/oddports.php">port numbers used by Trojans</uri>.</para>
 
     <para>FTP has two modes:  active mode and passive mode.  The
       difference is in how the data channel is acquired.  Passive
@@ -606,8 +606,8 @@ options         ALTQ_PRIQ       # Priority Queuing (PRIQ)</programlisting>
       </variablelist>
 
       <para>More information about the scheduling
-	algorithms and example rulesets are available at <uri
-	  xlink:href="http://www.openbsd.org/faq/pf/queueing.html">http://www.openbsd.org/faq/pf/queueing.html</uri>.</para>
+	algorithms and example rulesets are available at the <uri
+	  xlink:href="https://web.archive.org/web/20151109213426/http://www.openbsd.org/faq/pf/queueing.html">OpenBSD's web archive</uri>.</para>
     </sect2>
 
     <sect2 xml:id="pf-tutorial">
@@ -831,7 +831,7 @@ pass from { lo0, $localnet } to any keep state</programlisting>
     flags S/SA keep state</programlisting>
 
 	<para>A few other pass rules may be needed.  This one enables
-	  <acronym>SSH</acronym> on the external interface::</para>
+	  <acronym>SSH</acronym> on the external interface:</para>
 
 	<programlisting>pass in inet proto tcp to $ext_if port ssh</programlisting>
 
@@ -1009,7 +1009,7 @@ pass inet proto icmp from any to $ext_if keep state</programlisting>
 	<para>If other types of <acronym>ICMP</acronym> packets are
 	  needed, expand <literal>icmp_types</literal> to a list of
 	  those packet types.  Type <command>more
-	    /usr/src/contrib/pf/pfctl/pfctl_parser.c</command> to see
+	    /usr/src/sbin/pfctl/pfctl_parser.c</command> to see
 	  the list of <acronym>ICMP</acronym> message types supported
 	  by <application>PF</application>.  Refer to <link
 	      xlink:href="http://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml">http://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml</link>
@@ -1417,7 +1417,7 @@ rdr pass on $ext_if inet proto tcp from !&lt;spamd-white&gt; to \
 
 	    <para>When finished, reload the ruleset, start
 	      <application>spamd</application> by typing
-	      <command>service start obspamd</command>, and complete
+	      <command>service obspamd start</command>, and complete
 	      the configuration using <command>spamd-setup</command>.
 	      Finally, create a &man.cron.8; job which calls
 	      <command>spamd-setup</command> to update the tables at
@@ -1472,8 +1472,8 @@ rdr pass on $ext_if inet proto tcp from !&lt;spamd-white&gt; to \
 	  <step>
 	    <para>To complete the greylisting setup:</para>
 
-	    <programlisting>&prompt.root; <userinput>service restart obspamd</userinput>
-&prompt.root; <userinput>service start spamlogd</userinput></programlisting>
+	    <programlisting>&prompt.root; <userinput>service obspamd restart</userinput>
+&prompt.root; <userinput>service obspamlogd start</userinput></programlisting>
 	  </step>
 	</procedure>
 
@@ -2164,7 +2164,7 @@ pif="dc0"     # interface name of NIC attached to Internet</programlisting>
 	<acronym>LAN</acronym> should be assigned an
 	<acronym>IP</acronym> address in the private network space, as
 	defined by <link
-	  xlink:href="ftp://ftp.isi.edu/in-notes/rfc1918.txt">RFC
+	  xlink:href="https://www.ietf.org/rfc/rfc1918.txt">RFC
 	  1918</link>, and have the default gateway set to the
 	&man.natd.8; system's internal <acronym>IP</acronym>
 	address.</para>
@@ -2365,7 +2365,7 @@ good_tcpo="22,25,37,53,80,443,110"</programlisting>
 	  configuration file.</para>
 
 	<para>For further configuration options, consult
-	  &man.natd.8;</para>
+	  &man.natd.8;.</para>
       </sect3>
 
       <sect3>