Update parameter :version to 26.1 in several defcustom

Update parameter :version to 26.1 in several defcustom

Following defcustom where added or modified for 25.2 release.
In fact all these changes belong to 26.1 release.
* lisp/battery.el (battery-linux-sysfs-regexp)
* lisp/comint.el (comint-password-prompt-regexp)
* lisp/dired.el (dired-always-read-filesystem)
* lisp/image.el (image-scaling-factor)
* lisp/ibuf-ext.el (ibuffer-never-search-content-name)
(ibuffer-never-search-content-mode)
* lisp/mouse.el (mouse-select-region-move-to-beginning)
* lisp/net/net-utils.el (iwconfig-program, iwconfig-program-options)
(netstat-program, route-program, route-program-options)
* lisp/net/sieve-manage.el (sieve-manage-default-stream)
* lisp/progmodes/grep.el (grep-save-buffers)
* lisp/vc/add-log.el (change-log-directory-files)
* lisp/url/url-vars.el (url-user-agent)
* lisp/vc/vc-hg.el (vc-hg-symbolic-revision-styles)
(vc-hg-use-file-version-for-mode-line-version)
(vc-hg-parse-hg-data-structures)
* lisp/wdired.el (wdired-create-parent-directories)
* lisp/faces.el (homoglyph, nobreak-hyphen, read-multiple-choice-face)
* lisp/gnus/gnus-art.el (gnus-article-encrypt-protocol)
(gnus-button-url-regexp)
* lisp/window.el (switch-to-buffer-preserve-window-point)
* lisp/ibuffer.el (ibuffer-formats, ibuffer-locked-char)
(ibuffer-locked-buffer)
* lisp/textmodes/flyspell.el (flyspell-sort-corrections-function)
* lisp/emacs-lisp/edebug.el (edebug-sit-on-break)
* lisp/gnus/message.el (message-user-fqdn)
* lisp/simple.el (shell-command-dont-erase-buffer)
(extended-command-suggest-shorter)
* lisp/net/shr.el (shr-use-fonts)
* lisp/files.el (mounted-file-systems, kill-emacs-query-functions)