Add an optimized (and sign accurate) version of log1p (#1483)
Add an optimized (and sign accurate) version of log1p (#1483)

Relax the threshold for small arguments in expm1
OpenImageIO/oiio,OpenImageIO/oiio,lgritz/oiio,YangYangTL/oiio,OpenImageIO/oiio,lgritz/oiio,lgritz/oiio,YangYangTL/oiio,YangYangTL/oiio,YangYangTL/oiio,OpenImageIO/oiio,lgritz/oiio