tips in spec: write chi2 in plot

https://heasarc.gsfc.nasa.gov/xanadu/xspec/manual/XStclout.html

tclout stat
scan $xspec_tclout "%f" chistat
echo $chistat

tclout dof 1
scan $xspec_tclout "%d" dofd

setp com wi 2
setp com la f "chi2=$chistat dof=$dofd"