[ESS] [patch] ess-load-file not working with tramp-visited files and ess-remote

[Erik Iverson]

> One other point about the patch, which reflects my lack of understanding
> about how Emacs finds functions in its packages.
> 
> Should the patch have something to make sure tramp is
> available and loaded?  I don't know when tramp started shipping
> with Emacs, and even if it's present, does it have to be
> require'd before calling these functions?
> 
> Something like:
> 
> (when (require 'tramp)
>     ;; rest of patch )
> 
> ?

or maybe better:

(when (featurep 'tramp)
    ;; rest of patch)

since this will return t if tramp has already been loaded, which
I think is the only time we'd ever need to check if the file
we're sourcing is tramp controlled.

If we use require, it would load tramp when we don't have
to.