More FTP site arch stuff

[Ian Jackson <ijackson@chiark.chu.cam.ac.uk>]

I propose to add a link
  binary-i386 -> binary
to the stable, non-free and contrib trees on the FTP site.

This is so that the same code in dselect, mkpackages, dftp,
mkcontents, &c can be used to process all the trees, and so that the
same documentation for users can describe them.

Ian.

PS: Sorry about the large number of these silly little messages.