[Rd] Changes to correct problems with classes in namespaces

[John Chambers]

An extensive set of changes to the methods package has been committed
today to allow non-exported classes from packages with namespaces (and
some related fixes in dealing with generic functions from namespaces as
well).

The namespace mechanism requires packages to export any class
definitions that are part of the API.  Unfortunately, NOT exporting
classes has never really worked.

The problem was essentially that computations such as method dispatch
used the character-string name of a class, with no information about
where that class came from.  For non-exported classes, this caused many
computations down the line to fail.  Related problems came from not
using the generic function objects and the class definition objects.

The modified code passes the usual check and check-devel tests, plus
some tests for dealing with private classes, but if you have packages
that use methods extensively, please try these with the current r-devel
as soon as possible.

John
-- 
John M. Chambers                  jmc at bell-labs.com
Bell Labs, Lucent Technologies    office: (908)582-2681
700 Mountain Avenue, Room 2C-282  fax:    (908)582-3340
Murray Hill, NJ  07974            web: http://www.cs.bell-labs.com/~jmc