Change markdown-code-fontification buffer names to use "earmuffs"

[shipmints]

It would be nicer for markdown temporary buffers to have earmuffs as many people use conventional buffer filters that are set to filter buffers with names that conform to " *xxx*".

(defun markdown-fontify-code-block-natively (lang start end)
...
        (with-current-buffer
            (get-buffer-create
             (concat " markdown-code-fontification:" (symbol-name lang-mode)))
;; better as 
             (concat " *markdown-code-fontification:" (symbol-name lang-mode) "*")))