Also updated tests to reflect new show grants functionality.

The output is not completely correct due to recursive role grants not
being completly implemented. However, this will help with testing the
implementation of set role with recursive grants.

The function now performs a DEPTH FIRST SEARCH on the role graph.

At various key points: on_start, on_open, on_cycle, on_finish,
the function calls one of the corresponding functions passed as parameters.

function.

The function will be used to help print roles privileges recursively.

function.

The function will be used to help print roles privileges recursively.

function.

The function will be used to help print roles privileges recursively.

The privileges are not correctly updated via grant commands yet.

The bug was caused by not renaming the role if it was previously
modified by the handle_grant_struct(ROLE_ACL,...) call.

The same function used find_acl_role and would search for the already
renamed role when it handled ROLES_MAPPINGS_HASH. This caused it to not rename
the role/user correctly.

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.