Incorrect escaping prevented these from working as intended.
Found by relint.

* lisp/progmodes/cc-defs.el (c-search-backward-char-property):
Add missing backslash.
* lisp/progmodes/simula.el (simula-mode):
Remove one backslash too many.

Run "TZ=UTC0 admin/update-copyright $(git ls-files)".

In particular, with these unterminated quotes on each of two adjacent lines,
the following text was spuriously fontified with string face.

* lisp/progmodes/cc-defs.el
(c-search-backward-char-property-with-value-on-char): New macro.

* lisp/progmodes/cc-mode.el (c-clear-string-fences): Check whether there is an
unmatched quote at a lower buffer position which should match the current
quote, rather than wrongly assuming the latter is unmatched and marking it
with a punctuation syntax.
(c-font-lock-fontify-region): Ensure all pertinent parts of the buffer have
string fence properties applied before performing any syntactic operations on
it; in particular, this applies to a quote at an earlier buffer position which
"matches" one inside the region about to be fontified.

This fixes bug #4192.

* etc/NEWS: Add a new entry.

* lisp/progmodes/cc-defs.el (c-font-lock-flush): New macro.

* lisp/progmodes/cc-cmds.el (c-toggle-comment-style): On toggling the comment
style, invoke c-font-lock-flush when c-mark-wrong-style-of-comment is non-nil,
to cause that marking to be done instead on the other style of comment.

* lisp/progmodes/cc-fonts.el (c-maybe-font-lock-wrong-style-comments): New
function.
(c-cpp-matchers): Call c-maybe-font-lock-wrong-style-comments when
appropriate.

* lisp/progmodes/cc-vars.el (c-mark-wrong-style-of-comment): New customizable
option.

* doc/misc/cc-mode.texi (top level, Indentation Commands, Guessing the Style,
Custom Macros): For some opening quote marks, correct '' to ``.
(Minor Modes): Add an xref to the new page "Wrong Comment Style" in a
footnote.
(Wrong Comment Style): New page.

Also make miscellaneous amendments.

* lisp/progmodes/cc-align.el, lisp/progmodes/cc-cmds.el
* lisp/progmodes/cc-defs.el, lisp/progmodes/cc-engine.el
* lisp/progmodes/cc-langs.el, lisp/progmodes/cc-vars.el: Remove lots of
unneeded backslashes.

* lisp/progmodes/cc-langs.el (c-string-innards-re-alist): Remove redundant
"\\|\r" from regular expression.

* lisp/progmodes/cc-mode.el (c-make-mode-syntax-table): Correct the name of
the hook normal-erase-is-backspace-MODE-hook from a non-existant hook name.

* lisp/allout-widgets.el (allout-decorate-item-icon):
* lisp/emacs-lisp/chart.el (chart-goto-xy):
* lisp/forms.el (forms--make-format)
(forms--make-format-elt-using-text-properties):
* lisp/htmlfontify.el (hfy-unmark-trailing-whitespace):
* lisp/net/newst-plainview.el (newsticker-hide-entry)
(newsticker-show-entry):
* lisp/nxml/nxml-mode.el (nxml-cleanup):
* lisp/obsolete/longlines.el (longlines-unshow-hard-newlines)
(longlines-encode-region):
* lisp/org/ob-exp.el (org-babel-exp-process-buffer):
* lisp/org/org-agenda.el (org-agenda-show-new-time):
* lisp/progmodes/cc-defs.el
(c-clear-char-property-with-value-function)
(c-clear-char-property-with-value-on-char-function):
* lisp/progmodes/ebrowse.el (ebrowse--hide):
* lisp/progmodes/gdb-mi.el (gdb-send):
* lisp/progmodes/idlw-shell.el
(idlwave-retrieve-expression-from-level):
* lisp/progmodes/make-mode.el (makefile-fill-paragraph):
* lisp/progmodes/prog-mode.el (prettify-symbols--post-command-hook):
* lisp/progmodes/ruby-mode.el (ruby-syntax-propertize):
* lisp/tmm.el (tmm-remove-inactive-mouse-face):
Always pass an explicit plist to remove-text-properties.

* lisp/dired.el (dired--unhide):
* lisp/facemenu.el (facemenu-add-face):
* lisp/htmlfontify.el (hfy-fontify-buffer):
* lisp/iimage.el (iimage-mode-buffer):
* lisp/image-file.el (image-file-yank-handler):
* lisp/progmodes/prog-mode.el (prettify-symbols--compose-symbol):
* lisp/textmodes/tex-mode.el (latex-env-before-change):
* test/src/undo-tests.el (undo-test0):
Use remove-list-of-text-properties in place of
remove-text-properties where appropriate.

For this introduce the text property c-fl-syn-tab to "mirror" syntax-table.

* lisp/progmodes/cc-defs.el (c-is-escaped, c-will-be-escaped, c-put-syn-tab)
(c-clear-syn-tab, c-clear-syn-tab-properties, c-with-extended-string-fences):
new macros.
(c-point): Use c-is-escaped
(c-search-forward-char-property, c-search-backward-char-property)
(c-search-forward-char-property-with-value-on-char)
(c-search-forward-char-property-without-value-on-char): Fix regexp error
involving \n.

* lisp/progmodes/cc-engine.el (c-semi-pp-to-literal): User
c-with-extended-string-fences around a parse-partial-sexp.
(c-full-get-near-cache-entry): Fix an off-by-one error.
(c-full-pp-to-literal): Avoid writing duplicate entries into a cache.
(c-after-change-unmark-raw-strings): Use c-clear-syn-tab-properties.

* lisp/progmodes/cc-mode.el (c-leave-cc-mode-mode): Clear the c-fl-syn-tab
properties, too.
(c-basic-common-init): Mark c-fl-syn-tab as a non-sticky text property.
(c-depropertize-new-text): Also handle c-fl-syn-tab.
(c-multiline-string-check-final-quote, c-parse-quotes-after-change): Use
c-is-escaped.
(c-fl-syn-tab-region): New variable.
(c-clear-string-fences, c-restore-string-fences, c-remove-string-fences): New
functions.
(c-before-change-check-unbalanced-strings)
(c-after-change-mark-abnormal-strings, c-after-change-escape-NL-in-string):
Use the new functions and macros.
(c-before-change, c-after-change, c-font-lock-fontify-region): Restore the
syntax-table text properties from c-fl-syn-tab text properties for these
functions.
(c-electric-pair-inhibit-predicate): Test the c-fl-syn-tab property rather
than syntax-table.

* doc/misc/cc-mode.texi (top level, "Introduction"),
lisp/progmodes/cc-defs.el (c-version): Update version number to 5.34.

* lisp/progmodes/cc-defs.el (c-font-lock-flush): Delete this macro.

* lisp/progmodes/cc-engine.el (c-propertize-raw-string-opener): Delete the
call to the macro.