** If you have a program that makes several changes in the same area
of the buffer, you can use the macro combine-after-change-calls around that Lisp code to make it faster when after-change hooks are in use.

The macro arranges to call the after-change functions just once for a series of several changes--if that seems safe.

Don't alter the variables after-change-functions and after-change-function within the body of a combine-after-change-calls form.