ox-latex: Use :ALT_TITLE: on unnumbered headlines

* lisp/ox-latex.el (org-latex-headline): Use :ALT_TITLE: also on
  unnumbered headlines.

Suggested-by: Marcin Borkowski <mbork@wmi.amu.edu.pl>
<http://permalink.gmane.org/gmane.emacs.orgmode/96860>

lisp/ox-latex.el

@@ -1621,7 +1621,7 @@ holding contextual information."
 				  (org-string-match-p "\\<local\\>" v)
 				  (format "\\stopcontents[level-%d]" level)))))
 		    info t)))))
-	  (if (and numberedp opt-title
+	  (if (and opt-title
 		   (not (equal opt-title full-text))
 		   (string-match "\\`\\\\\\(.*?[^*]\\){" section-fmt))
 	      (format (replace-match "\\1[%s]" nil nil section-fmt 1)