3DSOLID: changed the return type for dxf_3dsolid_read().

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

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

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

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