The flag EXTRA_ACL is used in conjugation with our access checks, yet it is
not clear what impact this flag has.
This is a code clean up which replaces use of EXTRA_ACL with an explicit
function parameter.
The patch also fixes privilege checks for:
- SHOW CREATE TABLE: The new privilege requirement is any privilege on
  the table-level.
- CHECKSUM TABLE: Requires SELECT on the table level.
- SHOW CREATE VIEW: Requires SHOW_VIEW and SELECT on the table level
  (just as the manual claims)
- SHOW INDEX: Requires any privilege on any column combination.