(ITS#7386) back-mdb slapindex grows DB without bound

[hyc@OpenLDAP.org]

Full_Name: Howard Chu
Version: 2.4.32
OS: 
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (37.19.96.255)
Submitted by: hyc


mdb_tool_entry_next() keeps a read-only cursor open, which prevents free pages
from being reclaimed. Fix coming shortly.