Import back-mdb

doc/man/man5/slapd-mdb.5

servers/slapd/back-mdb/Makefile.in

servers/slapd/back-mdb/add.c

servers/slapd/back-mdb/attr.c

servers/slapd/back-mdb/back-mdb.h

servers/slapd/back-mdb/bind.c

servers/slapd/back-mdb/compare.c

servers/slapd/back-mdb/config.c

servers/slapd/back-mdb/delete.c

servers/slapd/back-mdb/dn2entry.c

servers/slapd/back-mdb/dn2id.c

servers/slapd/back-mdb/extended.c

servers/slapd/back-mdb/filterindex.c

servers/slapd/back-mdb/id2entry.c

servers/slapd/back-mdb/idl.c

servers/slapd/back-mdb/idl.h

servers/slapd/back-mdb/index.c

servers/slapd/back-mdb/init.c

servers/slapd/back-mdb/key.c

servers/slapd/back-mdb/modify.c