It seems that packages in ldap.studio jars import org.apache.commons.collections with restriction version >= 3.2.1. But, in org.apache.directory.api.ldap.model jar there is restriction for org.apache.commons.collections with version >= 3.2.0 < 4.0.0.
In most cases, where you have only one version of org.apache.commons.collections, this will work fine. But, in my situation i have 3.2.0 installed, as 3.2.1.
And Eclipse equinox have a problem with this, because it detects that not all requirements for org.apache.directory.* can be resolved in the consistent way, and it prevents loading of those classes. This results in LDAP browser or schema not working, in Eclipse.
Solution is quite easy - Import-Package directive in org.apache.directory.api.ldap.model jar needs to be changed to include only 3.2.1 or higher version of org.apache.commons.collection.
Since this bug prevents from LDAP working in Eclipse LUNO, this should be a critical bug.
I did manually change org.apache.directory.api.ldap.model jar, and can confirm that with this change, LDAP stuff is woring in LUNO.