Use "26.1" version string in Tramp, fix some comments

* lisp/net/tramp-gvfs.el (tramp-gvfs-methods):
* lisp/net/tramp-sh.el (tramp-remote-process-environment):
Use "26.1" version string.

lisp/net/tramp-compat.el

@@ -118,7 +118,7 @@ Add the extension of F, if existing."
 	 (extension (file-name-extension f t)))
     (make-temp-file prefix dir-flag extension)))
 
-;; `temporary-file-directory' as function is introduced with Emacs 25.2.
+;; `temporary-file-directory' as function is introduced with Emacs 26.1.
 (defalias 'tramp-compat-temporary-file-directory-function
   (if (fboundp 'temporary-file-directory)
       'temporary-file-directory

lisp/net/tramp-gvfs.el

@@ -114,7 +114,7 @@
   '("afp" "dav" "davs" "gdrive" "obex" "sftp" "synce")
   "List of methods for remote files, accessed with GVFS."
   :group 'tramp
-  :version "25.2"
+  :version "26.1"
   :type '(repeat (choice (const "afp")
 			 (const "dav")
 			 (const "davs")
@@ -1963,10 +1963,13 @@ They are retrieved from the hal daemon."
 
 ;; * Host name completion for existing mount points (afp-server,
 ;;   smb-server) or via smb-network.
+;;
 ;; * Check, how two shares of the same SMB server can be mounted in
 ;;   parallel.
+;;
 ;; * Apply SDP on bluetooth devices, in order to filter out obex
 ;;   capability.
+;;
 ;; * Implement obex for other serial communication but bluetooth.
 
 ;;; tramp-gvfs.el ends here

lisp/net/tramp-gw.el

@@ -331,6 +331,7 @@ password in password cache.  This is done for the first try only."
 ;;; TODO:
 
 ;; * Provide descriptive Commentary.
+;;
 ;; * Enable it for several gateway processes in parallel.
 
 ;;; tramp-gw.el ends here

lisp/net/tramp-sh.el

@@ -566,7 +566,7 @@ which might have been set in the init files like ~/.profile.
 Special handling is applied to the PATH environment, which should
 not be set here. Instead, it should be set via `tramp-remote-path'."
   :group 'tramp
-  :version "25.2"
+  :version "26.1"
   :type '(repeat string)
   :require 'tramp)
 

lisp/net/tramp-smb.el

@@ -2042,8 +2042,10 @@ Returns nil if an error message has appeared."
 ;;; TODO:
 
 ;; * Return more comprehensive file permission string.
+;;
 ;; * Try to remove the inclusion of dummy "" directory.  Seems to be at
 ;;   several places, especially in `tramp-smb-handle-insert-directory'.
+;;
 ;; * Ignore case in file names.
 
 ;;; tramp-smb.el ends here

lisp/net/tramp.el

@@ -1959,7 +1959,7 @@ ARGS are the arguments OPERATION has been called with."
    ;; COMMAND.
    ((member operation
 	    '(process-file shell-command start-file-process
-	      ;; Emacs 25.2+ only.
+	      ;; Emacs 26+ only.
 	      make-nearby-temp-file temporary-file-directory))
     default-directory)
    ;; PROC.