11/18/97: 

Grabbed Warren McLaughlin's acis_process_events_functions.c, as this
contains the implementation of both ASCA and ACIS grading schemes.
Requires implicit understanding of meaning of flight grades in terms of
event split geometry. See functions find_asca_grade and find_acis_grade
(also see his email, in this directory).

acis_process_events.h contains definition of strings (ACIS_GRADE_BLAH) in
terms of 0-N (integer) system.