argument/attribute missing in testbrowser tests.

  provided tests and implementation for guarded_zip (RestrictedPython).

- fixed the auth encoding classifier 

 - Add guards for 'all' and 'any', new in Python 2.5. Add support for 'key' keyword argument to 'max' and 'min' guards

for failed imports, obscuring later attempts to import the same broken module.

'AccessControl.ZopeGuards.guarded_import' mapped some Unauthorized exceptions
onto ImportErrors:  don't do that!  Also, removed mutable defaults from
argument list, improved tests.

 - Avoid raising string exceptions. If one is found, upgrade it to InternalError and keep the original exception name as part of exc_value

  2.6. Adjust tests accordingly.

  relative using new syntax so that they work on Python 2.6.