Change :version in defcustoms from "25.2" to "26.1"

Change :version in defcustoms from "25.2" to "26.1"

* lisp/ob-J.el (org-babel-J-command):
* lisp/ob-core.el (org-babel-hash-show-time):
* lisp/ob-exp.el (org-babel-exp-inline-code-template):
* lisp/ob-lisp.el (org-babel-lisp-eval-fn):
* lisp/org-agenda.el (org-agenda-view-columns-initially):
* lisp/org-attach.el (org-attach-commit):
(org-attach-archive-delete):
(org-attach-annex-auto-get):
* lisp/org-bibtex.el (org-bibtex-inherit-tags):
* lisp/org-clock.el (org-clock-into-drawer):
* lisp/org-colview.el (org-columns-summary-types):
* lisp/org-faces.el (org-block):
* lisp/org-src.el (org-src-block-faces):
* lisp/org-table.el (org-table-copy-increment):
(org-table-formula-create-columns):
(org-table-convert-region-max-lines):
* lisp/org-timer.el (org-timer-default-timer):
* lisp/org.el (org-export-backends):
(org-show-context-detail):
(org-cycle-hook):
(org-occur-case-fold-search):
(org-preview-latex-default-process):
(org-preview-latex-process-alist):
(org-preview-latex-image-directory):
(org-latex-default-packages-alist):
(org-sparse-tree-default-date-type):
(org-structure-template-alist):
(org-effort-durations):
(org-agenda-ignore-properties): Change :version from "25.2" to "26.1".
(customize-package-emacs-version-alist): Fix associations between Org
and Emacs releases.
* lisp/ox-ascii.el (org-ascii-list-margin):
* lisp/ox-beamer.el (org-beamer-subtitle-format):
* lisp/ox-html.el (org-html-format-headline-function):
(org-html-format-inlinetask-function):
(org-html-viewport):
* lisp/ox-latex.el (org-latex-caption-above):
(org-latex-prefer-user-labels):
(org-latex-subtitle-format):
(org-latex-hyperref-template):
(org-latex-footnote-defined-format):
(org-latex-images-centered):
(org-latex-default-figure-position):
(org-latex-text-markup-alist):
(org-latex-format-inlinetask-function):
(org-latex-custom-lang-environments):
(org-latex-compiler-file-string):
(org-latex-compiler):
(org-latex-bib-compiler):
(org-latex-logfiles-extensions):
(org-latex-known-warnings):
* lisp/ox-md.el (org-md-footnotes-section):
(org-md-footnote-format):
* lisp/ox-odt.el (org-odt-format-headline-function):
(org-odt-format-inlinetask-function):
(org-odt-inline-image-rules):
* lisp/ox-texinfo.el (org-texinfo-format-headline-function):
* lisp/ox.el (org-export-with-creator):
(org-export-with-title):
(org-export-with-broken-links):
(org-export-copy-to-kill-ring): Change :version from "25.2" to "26.1".

It looks like the goal is to sync Org 9.0.* (maint) with the Emacs
master branch (what will be version 26.1):
https://lists.gnu.org/archive/html/emacs-orgmode/2017-01/msg00558.html