[compat] Missing fs.existsSync on node v0.6.12

   Patch fs to get missing existsSync.
Support for multiple jshint-mode servers running in parallel (one per port)

  Allows multiple emacs programs to be open and benefit from jshint-mode
  at the same time. A server is started on the lowest unused port in the
  (configurable) range 3003 to 3100.

  The server gets a new argument --lastport INT. The flymake-hook filters
  stdout for the "Server started" message and extracts the port from there.
[flymake cursor] Convenience tool to show flymake errors in minibuffer