Use BIT(x) macro for better sync to staging comedi.h
Use BIT(x) macro for better sync to staging comedi.h

This patch defines a copy of the kernel BIT(x) macro and syncs the use of
BIT(x) between the staging tree and comedilib versions of comedi.h

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