Add missing dblink files.

contrib/dblink/doc/query

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+==================================================================
+Name
+
+dblink -- Returns a set from a remote database
+
+Synopsis
+
+dblink(text connstr, text sql)
+- or -
+dblink(text sql)
+
+Inputs
+
+  connstr
+
+    standard libpq format connection string, 
+    e.g. "hostaddr=127.0.0.1 port=5432 dbname=mydb user=postgres password=mypasswd"
+    If the second form is used, then the dblink_connect(text connstr) must be
+    executed first.
+
+  sql
+
+    sql statement that you wish to execute on the remote host
+    e.g. "select * from pg_class"
+
+Outputs
+
+  Returns setof record
+
+Example usage
+
+test=# select * from dblink('dbname=template1','select proname, prosrc from pg_proc')
+ as t1(proname name, prosrc text) where proname like 'bytea%';
+  proname   |   prosrc
+------------+------------
+ byteacat   | byteacat
+ byteaeq    | byteaeq
+ bytealt    | bytealt
+ byteale    | byteale
+ byteagt    | byteagt
+ byteage    | byteage
+ byteane    | byteane
+ byteacmp   | byteacmp
+ bytealike  | bytealike
+ byteanlike | byteanlike
+ byteain    | byteain
+ byteaout   | byteaout
+(12 rows)
+
+test=# select dblink_connect('dbname=template1');
+ dblink_connect
+----------------
+ OK
+(1 row)
+
+test=# select * from dblink('select proname, prosrc from pg_proc')
+ as t1(proname name, prosrc text) where proname like 'bytea%';
+  proname   |   prosrc
+------------+------------
+ byteacat   | byteacat
+ byteaeq    | byteaeq
+ bytealt    | bytealt
+ byteale    | byteale
+ byteagt    | byteagt
+ byteage    | byteage
+ byteane    | byteane
+ byteacmp   | byteacmp
+ bytealike  | bytealike
+ byteanlike | byteanlike
+ byteain    | byteain
+ byteaout   | byteaout
+(12 rows)
+
+==================================================================
+A more convenient way to use dblink may be to create a view:
+
+ create view myremote_pg_proc as
+ select *
+ from dblink('dbname=template1','select proname, prosrc from pg_proc')
+ as t1(proname name, prosrc text);
+
+Then you can simply write:
+
+   select * from myremote_pg_proc where proname like 'bytea%';
+