[Seisunix] SU Release 44R19

There are a few bug fixes. I have put in a few epidemiological modeling codes in regard to our current situation with the Coronavirus. These items may be of interest for those teaching ordinary differential equations. Also, this modeling approach could be modified for oil and gas field production modeling. John Stockwell Visit: https://wiki.Seismic-Unix.org The new home of Seismic Un*x