Ensure proper build on Apple Clang 6.1
Ensure proper build on Apple Clang 6.1

bdeluca/oiio,micler/oiio,OpenImageIO/oiio,OpenImageIO/oiio,lgritz/oiio,YangYangTL/oiio,bdeluca/oiio,OpenImageIO/oiio,micler/oiio,bdeluca/oiio,bdeluca/oiio,lgritz/oiio,lgritz/oiio,YangYangTL/oiio,micler/oiio,YangYangTL/oiio,OpenImageIO/oiio,lgritz/oiio,YangYangTL/oiio,micler/oiio