bug 5549: change to kohastructure.sql missing from commit 8cea8e5cc05075dc391194248d3...

bug 5549: change to kohastructure.sql missing from commit 8cea8e5cc05075dc391194248d31a54586389601

Also deletes earlier updatedatabase addition of lengthunit to avoid errors for people upgrading from stable (thanks Katrin for the idea)

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Checked creating a database from scratch and updating a database
with missing lengthunit column. Both worked without any problem.
If you update and have the column updatedatabase will report an error,
but the database will be ok.