You can migrate your instalations to Percona Server and use one of this two ways to connect MySQL to LDAP by PAM:
Full PAM plugin called auth_pam. This plugin uses dialog.so. It fully supports the PAM protocol with arbitrary communication between client and server.
Oracle-compatible PAM called auth_pam_compat. This plugin uses mysql_clear_password which is a part of Oracle MySQL client. It also has some limitations, such as, it supports only one password input. You must use “-p” option in order to pass the password to auth_pam_compat.
http://www.percona.com/doc/percona-pam-for-mysql/intro.html
We are using auth_pam_compat but you have to remember that client has to support Cleartext Client-Side Authentication Plugin