We have recently upgraded to build with OpenSSL 1.1.1 on several
platforms.  This means that the "system" versions of libraries like
LDAP and SASL can no longer be used (they link with other versions of
SSL)

This patch is for 5.7: add cmake options WITH_LDAP and WITH_SASL,
assuming these have been built with the same version of SSL libraries
used for the server.  Look up static (.a) libraries for LDAP, LBER,
and SASL, and link these into appropriate plugins.

We also enable some tests which were previously skipped because of
bad feature tests.

Change-Id: If5deba8ae593b2c666ce12fab6ac7827e41b4f99
(cherry picked from commit 83406d64ec84438ac6f8d28fe191b3d8a215bd15)