Chapter vs Appendix in Calc Guide

Because we are not including the proposed Chapters 15 and 16 in this
edition of the Calc Guide, I think we should change the designation
for Chapters 17, 18, 19 back to Appendix A, B, C, as in CG4.1. I plan
to make this change if I don't receive any major objections by
Saturday 28 December. (I realise this will require a quick check of
other chapters for references to them, which I can do.)

Jean