+/*
+ Create and initialise the rs[x].cutpoint_rdr casereaders. That is, the readers will
+ be created with width 5, ready to take the values (cutpoint, TP, FN, TN, FP), and the
+ reader will be populated with its final number of cases.
+ However on exit from this function, only CUTPOINT entries will be set to their final
+ value. The other entries will be initialised to zero.
+*/