Use lt_dlopenext instead of lt_dlopen (ITS#2437)

[sfrost@snowman.net]

Full_Name: Stephen Frost
Version: HEAD
OS: Linux
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (141.156.159.253)


Please modify the lt_dlopen() in servers/slapd/module.c to be lt_dlopenext(). 
lt_dlopenext() will check whatever your platform supports, including using .la
where it is present but makes it so that .la files are not needed on platforms
which do not need them.  This will make OpenLDAP more flexible by not depending
on the libtool garbage too (which adds a runtime dependency for -dev packages
under Debian, which can be a real problem).  If you'd like a patch I'd be happy
to supply one.