OBJECT: implemented DXF_DEBUG macros.

Signed-off-by: bert <bert.timmerman@xs4all.nl>
OBJECT: correction of a typo.

Signed-off-by: bert <bert.timmerman@xs4all.nl>
OBJECT: added dxf_object_free().

Signed-off-by: bert <bert.timmerman@xs4all.nl>