use xo_errx; fix a couple of error messages; give usage message when there is nothing to do
use xo_errx; fix a couple of error messages; give usage message when there is nothing to do

Juniper/libxo,xcllnt/libxo,allanjude/libxo,allanjude/libxo,gahr/libxo,gahr/libxo,Juniper/libxo,allanjude/libxo,xcllnt/libxo,xcllnt/libxo,allanjude/libxo,Juniper/libxo,gahr/libxo,xcllnt/libxo,Juniper/libxo,gahr/libxo