support nested curly bracket pairs in latex fragments.

http://lists.gnu.org/archive/html/emacs-orgmode/2014-06/msg01022.html

Index: org-8.2.7b/lisp/org-element.el
===================================================================
--- org-8.2.7b.orig/lisp/org-element.el
+++ org-8.2.7b/lisp/org-element.el
@@ -3026,7 +3026,12 @@ Assume point is at the beginning of the
 				   (looking-at latex-regexp))))
 		    (throw 'exit (nth 2 e)))))
 	      ;; None found: it's a macro.
-	      (looking-at "\\\\[a-zA-Z]+\\*?\\(\\(\\[[^][\n{}]*\\]\\)\\|\\({[^{}\n]*}\\)\\)*")
+	      (looking-at (concat
+			   "\\\\\\([a-zA-Z]+\\*?\\)"
+			   "\\(?:<[^<>\n]*>\\)*"
+			   "\\(?:\\[[^][\n]*?\\]\\)*"
+			   "\\(?:<[^<>\n]*>\\)*"
+			   "\\(" (org-create-multibrace-regexp "{" "}" 3) "\\)\\{1,3\\}"))
 	      0))
 	   (value (org-match-string-no-properties substring-match))
 	   (post-blank (progn (goto-char (match-end substring-match))
Index: org-8.2.7b/doc/org.texi
===================================================================
--- org-8.2.7b.orig/doc/org.texi
+++ org-8.2.7b/doc/org.texi
@@ -10168,6 +10168,9 @@ any @LaTeX{} environment will be handled
 @code{\begin} and @code{\end} statements appear on a new line, at the
 beginning of the line or after whitespaces only.
 @item
+Commands like \command[...]{...} or \command{...}; the curly brakets could be
+nested up to 3 levels.
+@item
 Text within the usual @LaTeX{} math delimiters.  To avoid conflicts with
 currency specifications, single @samp{$} characters are only recognized as
 math delimiters if the enclosed text contains at most two line breaks, is