Distribute the real source for some doc/misc manuals (bug#45143)

Distribute the real source for some doc/misc manuals (bug#45143)

* doc/misc/modus-themes.texi, doc/misc/org.texi:
Remove generated files from repository.
* doc/misc/Makefile.in: Add rules for building .texi from .org.
(ORG_SRC, abs_top_builddir, EMACS, emacs):
New variables.
(org_template): New template.
(orgclean): New phony target.
* Makefile.in (info): Depend on lisp.
* lisp/org/ox-texinfo.el (org-texinfo-export-to-texinfo-batch):
New function.
* doc/misc/org.org, doc/misc/org-setup.org: New files.
Import from https://code.orgmode.org d8e8a97a14.