Short description to update the current lib

1. Download new lib at https://www.phpcaptcha.org/
2. Update all files in the current folder
   EXCEPT the following files because of Admidio changes in the files:
    securimage_show.php
    config.inc.php
3. Delete the following files:
    example_form.ajax.php
    example_form.php
4. Delete folder "audio" because we don’t implement it and it uses much space
