intarray doc example fix

Hi list,

I noticed a very small problem in the intarray docs example.
Trying out the example gives below error, the example uses the wrong parameter for the given operator class:

db=# CREATE TABLE message (mid INT PRIMARY KEY, sections INT[]);
CREATE TABLE
db=# CREATE INDEX message_rdtree_idx ON message USING GIST (sections gist__int_ops(siglen=32));
ERROR:  unrecognized parameter "siglen"

I'm not familiar with emailing patches, diff of suggested fix is below.

thanks
Simon

diff --git a/doc/src/sgml/intarray.sgml b/doc/src/sgml/intarray.sgml
index dfe98279c0..7b809a3519 100644
--- a/doc/src/sgml/intarray.sgml
+++ b/doc/src/sgml/intarray.sgml
@@ -446,7 +446,7 @@
 CREATE TABLE message (mid INT PRIMARY KEY, sections INT[], ...);

 -- create specialized index with signature length of 32 bytes
-CREATE INDEX message_rdtree_idx ON message USING GIST (sections gist__int_ops(siglen=32));
+CREATE INDEX message_rdtree_idx ON message USING GIST (sections gist__intbig_ops(siglen=32));

 -- select messages in section 1 OR 2 - OVERLAP operator
 SELECT message.mid FROM message WHERE message.sections && '{1,2}';