added function to convert multiple samples to/from phys units
added function to convert multiple samples to/from phys units

Linux-Comedi/comedilib,olsonse/comedilib,olsonse/comedilib,olsonse/comedilib,Linux-Comedi/comedilib,Linux-Comedi/comedilib,olsonse/comedilib,olsonse/comedilib,Linux-Comedi/comedilib,Linux-Comedi/comedilib,olsonse/comedilib,Linux-Comedi/comedilib