Hardcode "max-cache-size" for the "_bind" view

The built-in "_bind" view does not allow recursion and therefore does
not need a large cache database.  However, as "max-cache-size" is not
explicitly set for that view in the default configuration, it inherits
that setting from global options.  Set "max-cache-size" for the built-in
"_bind" view to a fixed value (2 MB, i.e. the smallest allowed value) to
prevent needlessly preallocating memory for its cache RBT hash table.

bin/named/config.c

@@ -263,6 +263,7 @@ view \"_bind\" chaos {\n\
 	recursion no;\n\
 	notify no;\n\
 	allow-new-zones no;\n\
+	max-cache-size 2M;\n\
 \n\
 	# Prevent use of this zone in DNS amplified reflection DoS attacks\n\
 	rate-limit {\n\