As suggested by Howard, I'm posting here what have been originally submitted as an ITS: http://www.OpenLDAP.org/its/index.cgi?findid=7283

Basically, some openldap header files not installed, hence considered as private seems to be needed for building out of tree extensions, such as ppolicy external password: checker (http://ltb-project.org/wiki/documentation/openldap-ppolicy-check-password).

According to howard, at least one of them (slap.h) seems to be mostly useless in this specific case, and could be avoided. The other one, tough (portable.h) seems unavoidable...