The up-to-date master copies of those documents are found in the
xorg-docs module, and posted on the X.Org website.

Also, x-docs.org no longer carries X11 docs, so point to X.Org's
website instead in the README.

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Daniel Stone <daniel@fooishbar.org>