Further fix privileges on pg_statistic_ext[_data].

We don't need to restrict column privileges on pg_statistic_ext;
all of that data is OK to read publicly.  What we *do* need to do,
which was overlooked by 6cbfb784c, is revoke public read access on
pg_statistic_ext_data; otherwise we still have the same security
hole we started with.

Catversion bump to ensure that installations calling themselves
beta2 will have this fix.

Diagnosis/correction by Dean Rasheed and Tomas Vondra, but I'm
going to go ahead and push this fix ASAP so we get more buildfarm
cycles on it.

Discussion: https://postgr.es/m/8833.1560647898@sss.pgh.pa.us

src/backend/catalog/system_views.sql

@@ -290,9 +290,8 @@ CREATE VIEW pg_stats_ext WITH (security_barrier) AS
                 WHERE NOT has_column_privilege(c.oid, a.attnum, 'select') )
     AND (c.relrowsecurity = false OR NOT row_security_active(c.oid));
 
-REVOKE ALL on pg_statistic_ext FROM public;
-GRANT SELECT (tableoid, oid, stxrelid, stxname, stxnamespace, stxowner, stxkeys, stxkind)
-    ON pg_statistic_ext TO public;
+-- unprivileged users may read pg_statistic_ext but not pg_statistic_ext_data
+REVOKE ALL on pg_statistic_ext_data FROM public;
 
 CREATE VIEW pg_publication_tables AS
     SELECT

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201906152
+#define CATALOG_VERSION_NO	201906161
 
 #endif