Adjust default value of "max-recursion-queries"

Since the queries sent towards root and TLD servers are now included in
the count (as a result of the fix for CVE-2020-8616),
"max-recursion-queries" has a higher chance of being exceeded by
non-attack queries.  Increase its default value from 75 to 100.

(cherry picked from commit ab0bf49203)

CHANGES

@@ -1,3 +1,6 @@
+5541.	[func]		Adjust the "max-recursion-queries" default from 75 to
+			100. [GL #2305]
+
 5540.	[port]		Fix building with native PKCS#11 support for AEP Keyper.
 			[GL #2315]
 

bin/named/config.c

@@ -185,7 +185,7 @@ options {\n\
 	max-clients-per-query 100;\n\
 	max-ncache-ttl 10800; /* 3 hours */\n\
 	max-recursion-depth 7;\n\
-	max-recursion-queries 75;\n\
+	max-recursion-queries 100;\n\
 	message-compression yes;\n\
 #	min-roots <obsolete>;\n\
 	minimal-any false;\n\

doc/arm/Bv9ARM-book.xml

@@ -9299,7 +9299,7 @@ avoid-v6-udp-ports { 40000; range 50000 60000; };
 		  This sets the maximum number of iterative queries that
 		  may be sent while servicing a recursive query.
 		  If more queries are sent, the recursive query
-		  is terminated and returns SERVFAIL.  The default is 75.
+		  is terminated and returns SERVFAIL.  The default is 100.
 		</para>
 	      </listitem>
 	    </varlistentry>

doc/arm/Bv9ARM.ch06.html

@@ -7115,7 +7115,7 @@ avoid-v6-udp-ports { 40000; range 50000 60000; };
                   This sets the maximum number of iterative queries that
                   may be sent while servicing a recursive query.
                   If more queries are sent, the recursive query
-                  is terminated and returns SERVFAIL.  The default is 75.
+                  is terminated and returns SERVFAIL.  The default is 100.
                 </p>
               </dd>
 <dt><span class="term"><span class="command"><strong>notify-delay</strong></span></span></dt>

doc/arm/notes-9.11.26.xml

@@ -55,7 +55,14 @@
     <itemizedlist>
       <listitem>
         <para>
-          None.
+          Adjust the <command>max-recursion-queries</command> default
+          from 75 to 100. Since the queries sent towards root and
+          TLD servers are now included in the count (as a result
+          of the fix for CVE-2020-8616),
+          <command>max-recursion-queries</command> has a higher
+          chance of being exceeded by non-attack queries, which is
+          the main reason for increasing its default value. [GL
+          #2305]
         </para>
       </listitem>
     </itemizedlist>

lib/dns/resolver.c

@@ -169,8 +169,8 @@
 
 /* The default maximum number of iterative queries to allow before giving up. */
 #ifndef DEFAULT_MAX_QUERIES
-#define DEFAULT_MAX_QUERIES 75
-#endif
+#define DEFAULT_MAX_QUERIES 100
+#endif /* ifndef DEFAULT_MAX_QUERIES */
 
 /*
  * After NS_FAIL_LIMIT attempts to fetch a name server address,