allow square brackets in emphasis post-match

* lisp/org.el (org-emphasis-regexp-components): Allow square brackets
  in the emphasis post match.

lisp/org.el

@@ -4269,7 +4269,7 @@ After a match, the match groups contain these elements:
 ;; set this option proved cumbersome.  See this message/thread:
 ;; http://article.gmane.org/gmane.emacs.orgmode/68681
 (defvar org-emphasis-regexp-components
-  '(" \t('\"{" "- \t.,:!?;'\")}\\" " \t\r\n,\"'" "." 1)
+  '(" \t('\"{" "- \t.,:!?;'\")}\\\[" " \t\r\n,\"'" "." 1)
   "Components used to build the regular expression for emphasis.
 This is a list with five entries.  Terminology:  In an emphasis string
 like \" *strong word* \", we call the initial space PREMATCH, the final