[R] update to posting guide: use 'sessionInfo()' instead of 'version'

[Seth Falcon]

I think using sessionInfo() instead of version is a good idea.

On 29 Dec 2005, tplate at acm.org wrote:
> [Note that sessionInfo() currently does not report all the
> information that 'version' does (it omits at least "Status" and "svn
> rev").  R-core members are aware of this -- whether or not they
> change this is up to them.]

Another thing not currently reported by sessionInfo() is a list of
loaded name spaces.  As more packages use name spaces and importing
dependencies instead of attaching them, this will become useful debug
info.

Loaded name spaces can be listed using loadedNamespaces().

+ seth