GN_Cls, Classify character

IN:
     A = character to classify
OUT:
     F = flags indicate classification, as follows:
          Fc = 0, Fz = 0: Neither alphabetic or numeric
          Fc = 0, Fz = 1: Numeric ('0' ... '9')
          Fc = 1, Fz = 0: Upper case letter ('A' ... 'Z')
          Fc = 1, Fz = 1: Lower case letter ('a' ... 'z')

Registers changed after return:
     A.BCDEHL/IXIY same
     .F....../.... different