Fix accidential change in tramp-tests; do not merge with master
* lisp/net/trampver.el: Change version to "2.3.5.26.3". (customize-package-emacs-version-alist): Add Tramp version integrated in Emacs 26.3. * test/lisp/net/tramp-tests.el (tramp-test42-auto-load): Add skip for w32.