Some trivial optimzations

Check if AND/OR expression can be NULL; Fixed bug in GROUP BY and-or-expression where expression could be NULL
Bug fix for SHOW OPEN TABLES when user didn't have privilege to access all open tables.
Better fix for ALTER TABLE on BDB tables.

mysql-test/r/bdb-alter-table-2.result

@@ -1,4 +1,6 @@
+select * from t1;
 objid	tablename	oid
 1	t1	4
 2	metatable	1
 3	metaindex	1
+drop table t1;