Import ksp's changes to support newer versions of DB2 (ITS#27).

CHANGES

include/ldbm.h

libraries/libldbm/ldbm.c

servers/slapd/back-ldbm/dbcache.c

servers/slapd/back-ldbm/dn2id.c

servers/slapd/back-ldbm/id2children.c

servers/slapd/back-ldbm/id2entry.c

servers/slapd/back-ldbm/idl.c

servers/slapd/back-ldbm/index.c

servers/slapd/tools/centipede.c

servers/slapd/tools/ldbmcat.c

servers/slapd/tools/ldbmtest.c

servers/slapd/tools/ldif2id2children.c

servers/slapd/tools/ldif2id2entry.c

servers/slapd/tools/ldif2ldbm.c

servers/slapd/tools/sizecount.c