memory leaks with threads disabled (ITS#3155)

[estokes@symas.com]

Full_Name: Eric Stokes
Version: Head
OS: linux
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (67.115.65.234)


When slapd is built with threading turned off, it
will leak ~1MB/sec under a 2-5 op per second load.
With threading turned back on the leak disappears.