Fix #103: Do not use functions unknown to GNU emacs

We don't have to depend on CL package, yet

lisp/mastodon-toot.el

@@ -147,9 +147,9 @@ Set `mastodon-toot--content-warning' to nil."
 (defun mastodon-toot--get-mode-kbinds ()
   "Get a list of the keybindings in the mastodon-toot-mode."
   (let* ((binds (copy-tree mastodon-toot-mode-map))
-	 (prefix (caadr binds))
-	 (bindings (remove-if-not (lambda (x) (listp x))
-				  (cadr binds))))
+	 (prefix (car (cadr binds)))
+	 (bindings (remove nil (mapcar  (lambda (i) (if (listp i) i))
+					(cadr binds)))))
     (mapcar (lambda (b)
 	      (progn
 		(setf (car b) (vector prefix (car b)))
@@ -174,7 +174,7 @@ e.g. mastodon-toot--send -> Send."
 
 (defun mastodon-toot--format-kbinds (kbinds)
   "Format a list keybindings, KBINDS, for display in documentation."
-  (string-join (cons "" (mapcar #'mastodon-toot--format-kbind kbinds))
+  (mapconcat 'identity (cons "" (mapcar #'mastodon-toot--format-kbind kbinds))
 	       "\n"))
 
 (defun mastodon-toot--make-mode-docs ()