bug#3921: 23.1.50; checkdoc allow uncapitalized info node links

[Kevin Ryde]

M-x checkdoc on the file foo.el below complains

    Name emacs should appear capitalized as Emacs (C-h,f,e,n,p,q)

at the `(emacs)' info link.  I hoped it would recognise that has to be
left as-is, since it must follow the target document's name and nodes.

Perhaps the following, dragging in help-mode.el for a definitive regexp,
and using thingatpt.el just because it's a convenient way to match
surrounding point.

2009-07-25  Kevin Ryde  <user42@zip.com.au>

        * emacs-lisp/checkdoc.el (checkdoc-proper-noun-region-engine): Allow
        uncapitalized in info node hyperlinks.

foo.el
Description: application/emacs-lisp

checkdoc.el.info-link.diff
Description: Text Data

In GNU Emacs 23.1.50.4 (i586-pc-linux-gnu, GTK+ Version 2.16.4)
 of 2009-07-24 on blah.blah
configured using `configure  'CFLAGS=-O -g' '--prefix=/down/emacs/b/inst' 
'--with-x-toolkit=gtk''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_AU
  value of $XMODIFIERS: nil
  locale-coding-system: iso-latin-1-unix
  default-enable-multibyte-characters: t