bug#13945: `abreviated-home-dir' isn't documented

[Xue Fuqiao]

In the source code of `command-line':

  ;; Force recomputation, in case it was computed during the dump.
  (setq abbreviated-home-dir nil)

The variable `abbreviated-home-dir' (which is defined in files.el) is
not documented in elisp manual. (Maybe there isn't a need?)

BTW what does the expression above do?  I had searched loadup.el and
some other files in `lisp/', but I didn't find anything useful.

-- 
Best regards, Xue Fuqiao.
http://www.emacswiki.org/emacs/XueFuqiao