Added CTL script for RedHat linux.

This allows to use anonymous bind, if binddn is not provided. Previous
default setting lead to use of unauthenticated bind, which is usually
disabled in LDAP server configurations.

Standardizing representation of hyperlink to "How Authentication Works in the Reference Implementation" section of blog post. Adding space in front of OpenLDAP hyperlink in 'Compatibility' section, hoping that makes the link look right.

Correcting link to blog post: changing https://nginx.com/blog/nginx-plus-authenticate-users#configure to .../#ldap-auth-configure