Add context info to OAT_POST_CREATE security hook

... and have sepgsql use it to determine whether to check permissions
during certain operations.  Indexes that are being created as a result
of REINDEX, for instance, do not need to have their permissions checked;
they were already checked when the index was created.

Author: KaiGai Kohei, slightly revised by me

src/backend/bootstrap/bootparse.y

@@ -247,7 +247,8 @@ Boot_CreateStmt:
 													  ONCOMMIT_NOOP,
 													  (Datum) 0,
 													  false,
-													  true);
+													  true,
+													  false);
 						elog(DEBUG4, "relation created with OID %u", id);
 					}
 					do_end();