backport: erc bugfixes
Replace doc/*/Makefile.in dist rules with code in admin/admin.el

* admin/admin.el (make-manuals-dist-output-variables)
(make-manuals-dist--1, make-manuals-dist): New.
Replaces doc/*/Makefile.in `dist' rules.

* doc/emacs/Makefile.in (version): Remove variable.
(clean): No longer delete dist tarfile.
(dist): Remove rule; replace with code in admin.el.

* doc/lispintro/Makefile.in (version): Remove variable.
(clean): No longer delete dist tarfile.
(dist): Remove rule; replace with code in admin.el.

* doc/lispref/Makefile.in (version): Remove variable.
(clean): No longer delete dist tarfile.
(dist): Remove rule; replace with code in admin.el.

* doc/misc/Makefile.in (version): Remove variable.
(clean): No longer delete dist tarfile.
(dist): Remove rule; replace with code in admin.el.