[Rd] Suggestion: Add links to NEWS and CHANGES on help.start() page

[Henrik Bengtsson]

Hi,

right now it is actually a bit tricky to locate and view the NEWS and
the CHANGES files, especially if you are a beginning and don't even
know that you are supposed to look for them.

I'd like to recommend that links to (local) NEWS and CHANGES are added
to the help.start() overview pages.  help("NEWS")/help("CHANGE LOG")
and help("CHANGES") could display/refer to them as well.

/Henrik