These came to light in the contexts of bug#29713 and bug#47234.

* lisp/emulation/edt-mapper.el (edt-xserver):
* lisp/emulation/edt.el (edt-xserver):
* lisp/gnus/gnus-util.el (gnus-rescale-image):
* lisp/gnus/nnimap.el (nnimap-map-port):
* lisp/term/w32-win.el:
* lisp/image.el (image--get-imagemagick-and-warn):
* lisp/frame.el (frame-notice-user-settings): Declare functions that
are known to be present at runtime in GUI builds.
(make-frame-on-display): Signal more informative error when called
interactively in a non-GUI build (bug#29713).
* lisp/international/mule-diag.el (describe-font):
* lisp/org/org-macs.el (org--string-from-props): Pacify warnings
about unknown functions in non-GUI bilds.
* lisp/mh-e/mh-mime.el (mh-small-image-p): Avoid eliminating fboundp
check in non-GUI builds, to pacify unused lexical variable warning.
* lisp/net/newst-plainview.el (newsticker--plainview-tool-bar-map):
* lisp/net/newst-treeview.el (newsticker-treeview-tool-bar-map):
Declare tool-bar-map as a special variable in non-GUI builds.

This change has already been made on org-mode's master branch.

* lisp/org/org-install.el:
* lisp/org/org-version.el: Use lexical-binding.

* lisp/org/ob-lilypond.el (org-babel-lilypond-compile-lilyfile):
Remove always-nil variable `arg-2`.

* lisp/org/ol-gnus.el (org-gnus-store-link):
Remove always-nil variables `newsgroup` and `xarchive`.

* lisp/org/ol.el (org-store-link):
Remove always-nil variable `description`.

* lisp/org/org-clock.el (org-clock-special-range):
Remove always-nil variables `m1` and `m`.

* lisp/org/org-crypt.el (org--matcher-tags-todo-only): Declare var.

* lisp/org/org-protocol.el (org-protocol-open-source):
Remove always-nil variable `result`.

* lisp/org/ox-odt.el (org-odt-format-label):
Remove always-nil variable `short-caption`.
(org-odt-link--inline-formula):
Remove always-nil variables `width` and `height`.

* lisp/org/ox.el (org-export--missing-definitions):
Remove always-nil variable `seen`.

* doc/misc/Makefile.in (org_template): Don't delete output.
* lisp/org/ox-texinfo.el (org-texinfo-export-to-texinfo-batch):
Overwrite existing output.

* lisp/cedet/ede/dired.el:
* lisp/dired-x.el:
* lisp/filesets.el:
* lisp/follow.el:
* lisp/gnus/gnus-registry.el:
* lisp/net/eudc.el:
* lisp/printing.el:
* lisp/recentf.el:
* lisp/speedbar.el: Remove redundant require of easymenu; it is now
preloaded.
* lisp/org/org.el:
* lisp/progmodes/antlr-mode.el:
* lisp/progmodes/vhdl-mode.el:
* lisp/textmodes/reftex.el: Don't require easymenu in Emacs 28 or
later.

* etc/NEWS: Announce that 'easymenu' is now preloaded.

* lisp/allout.el:
* lisp/net/eudc.el:
* lisp/org/org.el: Don't require overlay; that's only needed in
XEmacs.

* 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.

While at it, I enabled lexical-binding in the affected files.

* lisp/cedet/semantic/sb.el: Enable lexical-binding.
(semantic-sb-with-tag-buffer): Use `declare`.

* lisp/cedet/semantic/bovine/el.el: Enable lexical-binding.
(semantic-elisp-setup-form-parser): Use `declare`.

* lisp/emacs-lisp/ert.el:
* lisp/emacs-lisp/ert-x.el: Remove redundant `put`.

* lisp/emulation/cua-rect.el: Enable lexical-binding.
(cua--rectangle-operation, cua--rectangle-aux-replace): Use `declare`.

* lisp/mh-e/mh-acros.el: Enable lexical-binding.
(mh-do-in-gnu-emacs, mh-do-in-xemacs, mh-funcall-if-exists, defun-mh)
(defmacro-mh, with-mh-folder-updating, mh-in-show-buffer)
(mh-do-at-event-location, mh-iterate-on-messages-in-region)
(mh-iterate-on-range): Use `declare`.

* lisp/mh-e/mh-compat.el: Enable lexical-binding.
(mh-flet): Use `declare`.

* lisp/mh-e/mh-e.el: Enable lexical-binding.
(defgroup-mh, defcustom-mh, defface-mh): Use `declare`.

* lisp/net/sieve.el: Enable lexical-binding.  Remove redundant :group args.
(sieve-activate, sieve-remove, sieve-edit-script): Remove unused arg
from the interactive spec.
(sieve-deactivate-all): Remove unused var `name`.
(sieve-change-region): Use `declare`.

* lisp/obsolete/fast-lock.el: Enable lexical-binding.
Remove redundant :group args.  Remove XEmacs compat code.
(save-buffer-state): Remove macro.
(fast-lock-add-properties): Use `with-silent-modifications` instead.

* lisp/obsolete/lazy-lock.el: Enable lexical-binding.
Remove redundant :group args.
(do-while): Use `declare`.
(save-buffer-state): Remove macro.
(lazy-lock-fontify-rest-after-change, lazy-lock-defer-line-after-change)
(lazy-lock-defer-rest-after-change, lazy-lock-after-fontify-buffer)
(lazy-lock-after-unfontify-buffer, lazy-lock-fontify-region):
Use `with-silent-modifications` instead.

* lisp/obsolete/pgg.el: Enable lexical-binding.  Remove XEmacs compat code.
(pgg-save-coding-system, pgg-as-lbt, pgg-process-when-success):
Use `declare`.
(pgg-add-passphrase-to-cache): Remove unused var `new-timer`.
(pgg-decrypt-region): Remove unused var `buf`.

* lisp/org/org-agenda.el (org-let, org-let2): Move from org-macs and
use `declare`.

* lisp/org/org-macs.el (org-let, org-let2): Move these functions that
are inherently harmful to your karma to the only package that uses them.
(org-scroll): Use `pcase` to avoid `eval` and use more readable syntax
for those integers standing for events.

* lisp/progmodes/antlr-mode.el: Enable lexical-binding.
(save-buffer-state-x): Use `declare` and `with-silent-modifications`.

* lisp/international/mule-util.el (with-coding-priority):
* lisp/cedet/ede/proj-comp.el (proj-comp-insert-variable-once):
* lisp/org/org-element.el (org-element-map):
* test/lisp/emacs-lisp/bytecomp-tests.el (test-byte-comp-compile-and-load):
* test/lisp/emacs-lisp/generator-tests.el (cps-testcase): Use `declare`.