We will no longer support full documentation generation from executables
and will instead generate documentation with other tools.  Disable (with
a warning left behind) the command-line options:

 --copyright
 --help-compatcommands
 --help-full
 --help-html
 --help-man

Drop supporting code.  Drop manual sections generation from executables.
Remove internal documentation construction APIs.  Drop unused sections
See Also, Author, Copyright, Compat Commands, Custom Modules.