SHAPE: make strings translatable.

Signed-off-by: bert <bert.timmerman@xs4all.nl>
SHAPE: use DxfFile struct.

Signed-off-by: bert <bert.timmerman@xs4all.nl>
SHAPE: removed dxf_shape_write_lowlevel().

Signed-off-by: bert <bert.timmerman@xs4all.nl>
SHAPE: changed the return type for dxf_shape_read().

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