Unreferenced subroutines are nullified (not removed) in a subset font
Separate Interpreter struct from hb-ot-cff-common-private.hh in a set of four header files, augmented for CharString (CS):
hb-cff-interp-common-private.hh
hb-cff-interp-dict-common-private.hh
hb-cff-interp-cs-common-private.hh
hb-cff-interp-cs.hh
Interpreter runtime is separated off as a new struct InterpEnv sub-classed differently for Dict and CharString (CS)
Michiharu Ariza