I made several changes to the patch.

The whatsnew docs didn't format correctly: there's an extra space on all the lines after the first (a three space indent is apparently required there which I don't understand, but it is also our standard for docs).  Also none of the links work, because in the whatsnew document (unlike in the doc page itself) you have to fully qualify the names (eg: ~http.cookies.Morsel to display 'Morsel' and link to the right place).  The line about LegalChars was in the wrong section.  I rewrote both as a single bullet item with working links.

The 'update' and 'copy' methods were not documented.  I added them and moved the relevant 'versionchanged' phrases under the newly documented methods.

In addition, I decided that the deprecation for key, value, and coded_value would be clearer if phrased as : "assignment to XXX; use set instead".

A couple of other notes: while functionally it doesn't (currently) make any difference to Sphinx if you use :func: vs :meth:, :meth: is the correct one for all these cases.  And you had an extra blank line after the versionchanged directive.

I've uploaded the changeset I applied as a diff so that you can more easily see what I changed if you wish.