fix sraw, srawi, srad, sradi instructions

fix sraw, srawi, srad, sradi instructions

For ISA 3.0 and beyond, the instructions also write the XER register.

Split the instructions out to a new command line option so we can create
an ISA 2.07 expect file, ISA 3.0 LE and ISA 3.0 BE expect file. The new
command line option is "-s" to just run just these four instructions.