Patch to keep the compatibility with xchat's coloring

diff --git a/lisp/riece-ctlseq.el b/lisp/riece-ctlseq.el
index b1bb87d..7cae37d 100644
--- a/lisp/riece-ctlseq.el
+++ b/lisp/riece-ctlseq.el
@@ -61,7 +61,7 @@
   "Mark up control sequences in IRC buffers.")
 
 (defconst riece-ctlseq-regexp
-  "[\x2\xF\x16\x1F]\\|\x3\\([0-9]+\\)?\\(,[0-9]+\\)?")
+  "[\x2\xF\x16\x1F]\\|\x3\\([0-9]\\{1,2\\}\\)?\\(,[0-9]\\{1,2\\}\\)?")
 
 (defun riece-ctlseq-compatible-attributes-p (this other)
   (let ((pointer this))