SPI specific: remove gcc4.8, C++11, old Boost
SPI specific: remove gcc4.8, C++11, old Boost

Also, we have a different script that controls building or Rez, there
is no need to clutter this here with Rez stuff we don't use.

OpenImageIO/oiio,lgritz/oiio,OpenImageIO/oiio,lgritz/oiio,OpenImageIO/oiio,OpenImageIO/oiio,lgritz/oiio,lgritz/oiio