erlang-xemacs-p removed from erlang-mode, breaks wrangler

[joedevivo]

erlang/otp#1411 removes the constant erlang-xemacs-p from erlang-mode, causing wrangler to crash on startup.

The quickest fix is for you to just define it yourself before loading wrangler:

(defconst erlang-xemacs-p (string-match "Lucid\\|XEmacs" emacs-version)
  "Non-nil when running under XEmacs or Lucid Emacs.")

According to erlang/otp#1411, xemacs support was removed, so it's probably worthwhile to remove it from wrangler as well. I'm happy to do it, just let me know if you'd like me to before I put the time in.