Fix '?#' character-macro syntax highlighting.

Try any example in which you use the '?#' built-in ASCII value syntax. You will see that the hashtag(#) is treated as a comment, although, this is not the case in Elixir. Also, the two lines which I altered appear to be redundant. The line in elixir-smie must be removed, otherwise, emacs will change the font-face as before, overridding the elixir-mode-font-lock-defaults.

Also, is there any reason why both of these lines existed concurrently?

Thanks.