Move all the generated file header printing into read_only_top()

Move all the generated file header printing into read_only_top()

Previously all the scripts in regen/ had code to generate header comments
(buffer-read-only, "do not edit this file", and optionally regeneration
script, regeneration data, copyright years and filename).

This change results in some minor reformatting of header blocks, and
standardises the copyright line as "Larry Wall and others".