Silence "unused <something>" warnings

servers/slapd/abandon.c

servers/slapd/ad.c

servers/slapd/back-bdb/cache.c

servers/slapd/back-bdb/config.c

servers/slapd/back-bdb/dn2id.c

servers/slapd/back-bdb/idl.c

servers/slapd/back-bdb/index.c

servers/slapd/back-bdb/init.c

servers/slapd/back-ldbm/close.c

servers/slapd/back-meta/candidates.c

servers/slapd/back-meta/compare.c

servers/slapd/back-meta/conn.c

servers/slapd/backover.c

servers/slapd/component.c

servers/slapd/controls.c

servers/slapd/ldapsync.c

servers/slapd/oc.c

servers/slapd/oidm.c

servers/slapd/phonetic.c

servers/slapd/root_dse.c