I left it out on purpose -- check the .info file. ldap should only be necessary if you are using mod_auth, and it has a large set of dependencies that I didn't see as necessary for general use (correct me if I'm wrong).
The mod_mysql_vhost module uses mysql.tcz, and mod_webdav uses libxml2.tcz and sqlite3.tcz. I wanted to include all the features I could, even the seldom-used ones, but including all those dependencies in lighttpd.tcz.dep made it not so light anymore. My compromise was to list them in the .info.