were accidentally removed during a previous rototill of this
code.  Fixes bug#27692.
  
While it can be argued we should strive to provide a 'secure by
default' installation, this happens to be the setup currently
documented in the manual as the default, so defer changes that
improve security out of the box to a co-ordinated effort later
on.
  
For now, make a note about the test databases and anonymous user
in mysql_install_db and recommend that mysql_secure_installation
be ran for users wishing to remove these defaults.

[..re-commit of previously lost change..]


scripts/mysql_system_tables_data.sql:
  Add anonymous accounts.
scripts/mysql_install_db.sh:
  Point users at the mysql_secure_installation script.
mysql-test/mysql-test-run.pl:
  Add a comment where removing anonymous users.