Corrections to imaging normalization at higher energies

There's been another change to hsi_calib_eventlist__define.pro to correct
the detector efficiency used to convert HESSI images from counts to photons.
Up to this point the detector efficiencies have been computed incorrectly by
assuming the detector consists of both front and rear segments instead of
either the front or rear segment alone.  And at this time the rest of the
software supports imaging using either the front or rear segments
exclusively to make images.  At energies up to 100 keV the effect is
negligible.  If you've made any front segment images above 100 keV, then
their true flux would be higher than previously reported.  If you've made
any rear segment images, then the flux of these would also be higher than
previously reported. For any images made in the front segment above 200 keV
the true flux may be up to a factor of two greater.  Since most images have
been made below 100 keV, most previous results would be little changed.

Again, sorry for the error but you will obtain the corrected version of
hsi_calib_eventlist__define.pro on your next update.

Regards

Richard Schwartz