not support roles

Also fixed issue with drop role not clearing internal memory entry
for that role. The issue was due to a condition introduced in handle_grant_data

Updated testsuite to also check the possible error conditions.

Revoke privilege on *.* to role@''; also works

Also added syntax for GRANT privilege TO { role } command

TODO: Use an index search on the table, instead of scanning through it.

This change only updates _in memory_ structures. 

Added extra comments to explain the ACL_USER_BASE flags usage, as well as fix an issue with get_role_access.

The bug caused roles rights to not be propagated if a push on the stack happened. The newly finished neighbour
was never reevaluated.

ACL_ROLE now inherits ACL_USER_BASE

Fixed possible failing condition due to different order of table rows

Moved fields corresponding to role entries to the ACL_ROLE class.

from the grant role to role graph.

resets the initial role access bits.