The ldap_init() function is marked as deprecated and not defined
by default on some systems. This can cause an error for compilers
that do not support implicit function declarations.
From Florian Weimer.
Wheh netgroup_base is set we now do out own netgroup lookups using
LDAP. Previously, LDAP was queried directly to get a list of the
netgroups the user belongs to but other netgroups queries went
through innetgr(3). This makes it possible to use netgroups
in LDAP sudoers on systems that don't have an innetgr() function.
GitHub issue #251.
This will find missing symbols at build-time instead of run-time.
Don't use it on FreeBSD where environ is filled in by the dynamic loader.
We also need to pull in -llber with -lldap where possible (instead
of relying on DT_NEEDED) to avoid undefined symbol errors when
building with LDAP support.
