Protect ditaa, r, R, and dot blocks from fontification

Since org-exp-blocks.el is now core, we protect these blocks from the
start.

lisp/org-src.el

@@ -109,11 +109,10 @@ or similar things which you want to have when editing a source code file,
 but which mess up the display of a snippet in Org exported files.")
 
 (defvar org-protecting-blocks
-  '("src" "example" "latex" "ascii" "html" "docbook")
+  '("src" "example" "latex" "ascii" "html" "docbook" "ditaa" "dot" "r" "R")
   "Blocks that contain text that is quoted, i.e. not processed as Org syntax.
 This is needed for font-lock setup.")
 
-
 ;;; Editing source examples
 
 (defvar org-src-mode-map (make-sparse-keymap))