SEQEND: according to R10..R14.

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

Signed-off-by: bert <bert.timmerman@xs4all.nl>
SEQEND: respect return value.

Signed-off-by: bert <bert.timmerman@xs4all.nl>
ARC: respect return value.

Signed-off-by: bert <bert.timmerman@xs4all.nl>
SHAPE: implemented DXF_DEBUG macros.

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