- Changed error message in sql_acl.cc
- Added some more tests for GRANT.


Docs/mysqld_error.txt:
  Added new error message.
mysql-test/r/grant2.result:
  Error message changed.
mysql-test/r/grant3.result:
  Clean up.
mysql-test/t/grant2.test:
  Error message changed.
sql/share/errmsg.txt:
  Added new error message.
sql/sql_acl.cc:
  Changed error message.
mysql-test/t/grant3.test:
  Error message changed.