This will be temporarilly used by the planner to mark consumption of
air at the surface. Do this by creating a new function add_cylinder,
which replaces add_to_cylinder_table() and takes care of always adding
a dummy cylinder at the end of the table. Make the original
add_to_cylinder_table() local, so that it cannot be accessed anymore.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
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