added back-sql files

servers/slapd/back-sql/Makefile.in

servers/slapd/back-sql/back-sql.h

servers/slapd/back-sql/backsql.dsp

servers/slapd/back-sql/bind.c

servers/slapd/back-sql/config.c

servers/slapd/back-sql/docs/bugs

servers/slapd/back-sql/docs/concept

servers/slapd/back-sql/docs/install

servers/slapd/back-sql/docs/platforms

servers/slapd/back-sql/entry-id.c

servers/slapd/back-sql/entry-id.h

servers/slapd/back-sql/external.h

servers/slapd/back-sql/init.c

servers/slapd/back-sql/modify.c

servers/slapd/back-sql/schema-map.h

servers/slapd/back-sql/sql-types.h