[Rd] I have corrected a dead link in the treering documentation

[Thomas Levine]

The attached patch corrects a dead link in the treering documentation.

The URL in the manual [1] refers to a personal home page belonging to
Christine Hallman (user "hallman") on the website of the University of
Arizona Laboratory of Tree-Ring Research (LTRR). It seems that the LTRR
personal homepages have been moved to a new root directory [2] and that
Hallman's webpage is no longer there.

I have contacted Dr. Hallman. She confirmed that the LTRR hosting has
changed and that she has not set up her website on a new host. Also,
I have not managed to find any other photographs of the Methuselah Walk.
So the page on the Wayback Machine [3] is the best option I see for now.

Dr. Hallman also told me that she has more photographs of the tree, and
she has offered to publish them in order that we may reference more
photographs eventually.

I have used approximately the following procedure to build and confirm
that the result is formatted properly. (I'm think all of these lines are
necessary, but I am not sure that this is the right order.)

  ./configure --without-recommended-packages
  cd src/library
  make all docs Rdfiles
  cd -
  make
  bin/R -e 'help(treering)'

I found other dead links in the base documentation, but I thought most
should be kept for reference, as they were usually links to a
publisher's webpage for a particular journal article or book. The link
of present interest just provides context about the tree whose rings
were measured, so I think it is okay to change the link.

[1] http://www.ltrr.arizona.edu/~hallman/sitephotos/meth.html
[2] http://www.ltrr.arizona.edu/webhome/
[3] https://web.archive.org/web/20110523225828/http://www.ltrr.arizona.edu/~hallman/sitephotos/meth.html
-------------- next part --------------
Index: src/library/datasets/man/treering.Rd
===================================================================
--- src/library/datasets/man/treering.Rd	(revision 72947)
+++ src/library/datasets/man/treering.Rd	(working copy)
@@ -32,6 +32,6 @@
 }
 \references{
   For some photos of Methuselah Walk see
-  \url{http://www.ltrr.arizona.edu/~hallman/sitephotos/meth.html}
+  \url{https://web.archive.org/web/20110523225828/http://www.ltrr.arizona.edu/~hallman/sitephotos/meth.html}
 }
 \keyword{datasets}