platform.h: move endian functions safely into OIIO namespace
platform.h: move endian functions safely into OIIO namespace

mcanthony/oiio,mcanthony/oiio,sambler/oiio,bdeluca/oiio,mcanthony/oiio,sambler/oiio,OpenImageIO/oiio,lgritz/oiio,bdeluca/oiio,YangYangTL/oiio,lgritz/oiio,cwilling/oiio,lgritz/oiio,bdeluca/oiio,sambler/oiio,OpenImageIO/oiio,OpenImageIO/oiio,bdeluca/oiio,micler/oiio,YangYangTL/oiio,cwilling/oiio,YangYangTL/oiio,sambler/oiio,lgritz/oiio,OpenImageIO/oiio,YangYangTL/oiio,cwilling/oiio,cwilling/oiio,mcanthony/oiio,micler/oiio,micler/oiio,micler/oiio