Made SGIImageReader padding fields public.
Made SGIImageReader padding fields public.

Clang doesn't like private fields which are never accessed.

goddardl/cortex,davidsminor/cortex,hradec/cortex,goddardl/cortex,appleseedhq/cortex,appleseedhq/cortex,davidsminor/cortex,hradec/cortex,lento/cortex,goddardl/cortex,lento/cortex,lento/cortex,davidsminor/cortex,davidsminor/cortex,appleseedhq/cortex,hradec/cortex