WL#2533: Implement "WITH GRANT OPTION"

Affects: Server-7.1   —   Status: Un-Assigned   —   Priority: Medium

Implement "GRANT OPTION" correctly - as an *option* of another privilege, not as
an independent privilege.

E.g. after

GRANT SELECT ON *.* TO foobar WITH GRANT OPTION;
GRANT INSERT ON *.* TO foobar;

foobar should be able to grant SELECT but not INSERT.