[v9_11] document that delv should be used instead of sigchase

(cherry picked from commit db93f3d4b3)

README

@@ -275,6 +275,7 @@ Building
 		Change the default syslog facility of named/lwresd.
 		  -DISC_FACILITY=LOG_LOCAL0
 		Enable DNSSEC signature chasing support in dig.
+		  (This feature is deprecated. Use `delv` instead.)
 		  -DDIG_SIGCHASE=1 (sets -DDIG_SIGCHASE_TD=1 and
 				    -DDIG_SIGCHASE_BU=1)
 		Disable dropping queries from particular well known ports.

bin/dig/dig.docbook

@@ -987,8 +987,9 @@
 	  <term><option>+[no]sigchase</option></term>
 	  <listitem>
 	    <para>
-	      Chase DNSSEC signature chains.  Requires dig be
-	      compiled with -DDIG_SIGCHASE.
+	      Chase DNSSEC signature chains. Requires dig be compiled
+	      with -DDIG_SIGCHASE. This feature is deprecated.
+	      Use <command>delv</command> instead.
 	    </para>
 	  </listitem>
 	</varlistentry>
@@ -1074,6 +1075,7 @@
 	    <para>
 	      When chasing DNSSEC signature chains perform a top-down
 	      validation.  Requires dig be compiled with -DDIG_SIGCHASE.
+	      This feature is deprecated. Use <command>delv</command> instead.
 	    </para>
 	  </listitem>
 	</varlistentry>
@@ -1127,6 +1129,7 @@
 	      directory.
 	    </para> <para>
 	      Requires dig be compiled with -DDIG_SIGCHASE.
+	      This feature is deprecated. Use <command>delv</command> instead.
 	    </para>
 	  </listitem>
 	</varlistentry>
@@ -1265,6 +1268,9 @@ dig +qr www.isc.org any -x 127.0.0.1 isc.org ns +noqr
   <refsection><info><title>SEE ALSO</title></info>
 
     <para><citerefentry>
+	<refentrytitle>delv</refentrytitle><manvolnum>1</manvolnum>
+      </citerefentry>,
+      <citerefentry>
 	<refentrytitle>host</refentrytitle><manvolnum>1</manvolnum>
       </citerefentry>,
       <citerefentry>