Add some missing version tags.

Add some missing version tags.

* lisp/electric.el (electric-quote-comment)
(electric-quote-string, electric-quote-paragraph):
* lisp/epg-config.el (epg-gpgconf-program):
* lisp/rect.el (rectangle-preview):
* lisp/emacs-lisp/check-declare.el (check-declare-ext-errors):
* lisp/emacs-lisp/package.el (package-selected-packages)
(package-hidden-regexps):
* lisp/erc/erc.el (erc-network-hide-list, erc-channel-hide-list):
* lisp/eshell/em-term.el (eshell-destroy-buffer-when-process-dies):
* lisp/gnus/mml-sec.el (mml1991-signers, mml2015-signers)
(mml-smime-signers, mml1991-encrypt-to-self, mml2015-encrypt-to-self)
(mml-smime-encrypt-to-self, mml2015-sign-with-sender)
(mml-smime-sign-with-sender, mml2015-always-trust)
(mml-secure-fail-when-key-problem, mml-secure-key-preferences):
* lisp/net/browse-url.el (browse-url-conkeror-new-window-is-buffer)
(browse-url-conkeror-arguments):
* lisp/net/newst-reader.el (newsticker-download-logos):
* lisp/progmodes/gud.el (gud-guiler-command-name):
* lisp/progmodes/prog-mode.el (prettify-symbols-unprettify-at-point):
* lisp/progmodes/project.el (project-vc):
* lisp/progmodes/python.el (python-indent-guess-indent-offset-verbose)
(python-shell-remote-exec-path, python-shell-first-prompt-hook)
(python-shell-completion-native-disabled-interpreters)
(python-shell-completion-native-enable)
(python-shell-completion-native-output-timeout)
(python-shell-completion-native-try-output-timeout):
* lisp/progmodes/xref.el (xref):
* lisp/term/screen.el (xterm-screen-extra-capabilities):
* lisp/term/xterm.el (xterm-max-cut-length):
Add missing version tags.