[ESS] several R versions

[Stephen Eglen]

Martin, Kaspar,

I just took a deeper look into R-devel, and found the problem.

If I have a program called "R-devel" on my path, I need to put the
following in .emacs BEFORE ess-site is loaded:

(setq ess-r-versions '("R-1" "R-2" "R-devel"))
(require 'ess-site)


since the R versions are created only on startup.  Perhaps I need to
document that better in the string.  This means also that if people
customize it, either:

1. their customize should come before ess-site is loaded (hard)

2. the customize code dynamically recreates R-versions (neater).


But if we change the default of ess-r-versions to the above, we should
be Okay for most people, especially you Martin, so you should be able
to remove your 6 year old function!

Please check and get back to me! 

Stephen