ob: keep \n inside of the code block body

* lisp/ob.el (org-babel-src-block-regexp): Keep the now-mandatory
  newline inside of the code block body.

lisp/ob.el

@@ -141,7 +141,7 @@ remove code block execution from the C-c C-c keybinding."
    ;; (4) header arguments
    "\\([^\n]*\\)\n"
    ;; (5) body
-   "\\([^\000]*?\n*\\)\n[ \t]*#\\+end_src")
+   "\\([^\000]*?\n\\)[ \t]*#\\+end_src")
   "Regexp used to identify code blocks.")
 
 (defvar org-babel-inline-src-block-regexp