[Rd] optional package dependency (enhances)

[Dirk Eddelbuettel]

A working system exists at 

	http://debian.cran.r-project.org 

with automated builds (ie automated resolutions of both built-time and
run-time dependencies) of over 2000 packages for both 64-bit Linux ("amd64")
and 32-bit Linux ("i386") of the Debian 'testing' distribution.  Charles and
I are not very proficient at publicising this but we fairly decent montly
downloads for something that is still 'beta' (in the Google sense).

The operating system will always have more local knowledge so here we are
trying to fold R's knowledge of its 2000 packages into the larger ecosystem
of the given Linux distributions.  Works for us, but it is a '2.0' approach
as an earlier one failed to scale.  I have made UseR presentations on each
one of these approaches.

Dirk

-- 
Three out of two people have difficulties with fractions.