bug #6933: error in the tests/grant.pl test).
mysql-test/r/grant.result:
A fix (bug #6932: 'revoke all privileges...' doesn't remove all proper columns from columns_priv).
mysql-test/t/grant.test:
A fix (bug #6932: 'revoke all privileges...' doesn't remove all proper columns from columns_priv).
sql/sql_acl.cc:
A fix (bug #6932: 'revoke all privileges...' doesn't remove all proper columns from columns_priv).
The problem is that we use whole key length (including 'Column_name' keypart)
during scanning the 'columns_priv' table in case of revoke_grant.
tests/grant.pl:
A fix (bug #6933: error in the tests/grant.pl test).
