Consider separators in computation of maximal mode width

Because the minor mode separators are added to the minor mode string
when filling, their size must be taken into account when computing the
maximal available width.

smart-mode-line.el

@@ -1520,11 +1520,15 @@ duplicated buffer names) from being displayed."
     (let* (;; The minor-mode-alist
            (nameList (rm--mode-list-as-string-list))
            ;; The size available
-           (size (if (member sml/mode-width '(full right))
-                     ;; Calculate how much width is available
-                     (sml/fill-width-available)
-                   ;; or use what the user requested.
-                   sml/mode-width))
+           (size (- (if (member sml/mode-width '(full right))
+                        ;; Calculate how much width is available
+                        (sml/fill-width-available)
+                      ;; or use what the user requested.
+                      sml/mode-width)
+                    (string-width (format-mode-line
+                                   'sml/pre-minor-modes-separator))
+                    (string-width (format-mode-line
+                                   'sml/pos-minor-modes-separator))))
            ;; Used for counting size.
            (finalNameList (mapconcat 'identity  nameList ""))
            needs-removing filling)
@@ -1546,11 +1550,7 @@ duplicated buffer names) from being displayed."
         (add-to-list 'nameList sml/propertized-shorten-mode-string t))
 
       ;; Padding
-      (setq filling (- size (length (format-mode-line
-                                     (list ""
-                                           'sml/pre-minor-modes-separator
-                                           nameList
-                                           'sml/pos-minor-modes-separator)))))
+      (setq filling (- size (length (format-mode-line nameList))))
       (setq filling (make-string (max 0 filling) sml/fill-char))
 
       (if (eq sml/mode-width 'right)