Add support for unsolicited notifications.

servers/slapd/Makefile.in

servers/slapd/abandon.c

servers/slapd/acl.c

servers/slapd/add.c

servers/slapd/ava.c

servers/slapd/back-bdb2/modify.c

servers/slapd/back-bdb2/search.c

servers/slapd/back-ldap/search.c

servers/slapd/back-ldbm/modify.c

servers/slapd/back-ldbm/search.c

servers/slapd/back-passwd/search.c

servers/slapd/back-perl/search.c

servers/slapd/back-shell/result.c

servers/slapd/back-tcl/tcl_util.c

servers/slapd/bind.c

servers/slapd/compare.c

servers/slapd/configinfo.c

servers/slapd/connection.c

servers/slapd/controls.c

servers/slapd/delete.c