org.el: Add grffile to default latex packages

* org.el (org-latex-default-packages-alist): Add grffile for files
  with spaces and periods.

Reported-by: Vaidheeswaran C <vaidheeswaran.chinnaraju@gmail.com>
<http://permalink.gmane.org/gmane.emacs.orgmode/97846>

lisp/org.el

@@ -4076,6 +4076,7 @@ header, or they will be appended."
     ("T1"   "fontenc"   t)
     (""     "fixltx2e"  nil)
     (""     "graphicx"  t)
+    (""     "grffile"   t)
     (""     "longtable" nil)
     (""     "float"     nil)
     (""     "wrapfig"   nil)