exec/rewrietmpicommand:
add README, modify ref2cmd.awk

change gwsrc/MPI_fpgw.F slightly
change main/hx0fp0.sc.m.F to switch MPI parallel x0kf_v4hz and non-MPI-paralle version.
logical:: BPMW=.true. use MPI parallel version.
(amend: add fpgw/exec/makefile)