ITS#3353 consolidate slapd globals into a single struct

servers/slapd/add.c

servers/slapd/back-bdb/compare.c

servers/slapd/back-bdb/delete.c

servers/slapd/back-bdb/init.c

servers/slapd/back-bdb/modify.c

servers/slapd/back-bdb/modrdn.c

servers/slapd/back-bdb/referral.c

servers/slapd/back-bdb/search.c

servers/slapd/back-dnssrv/referral.c

servers/slapd/back-dnssrv/search.c

servers/slapd/back-ldap/init.c

servers/slapd/back-ldbm/add.c

servers/slapd/back-ldbm/compare.c

servers/slapd/back-ldbm/delete.c

servers/slapd/back-ldbm/id2entry.c

servers/slapd/back-ldbm/modify.c

servers/slapd/back-ldbm/modrdn.c

servers/slapd/back-ldbm/referral.c

servers/slapd/back-ldbm/search.c

servers/slapd/back-meta/init.c