Filling removes hard newlines

[Jesper Harder]

Hard newlines are converted to soft newlines when filling paragraphs
(M-q) in text mode with use-hard-newlines turned on.

I think this is unintuitive, and it didn't happen in Emacs 21.2.

Steps to reproduce:

* Enter text-mode and turn on hard newlines.
* Type two paragraphs separated by a hard newline, say,

Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam
nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat,
sed diam voluptua.
At vero eos et accusam et justo duo dolores et ea rebum. Stet clita
kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit
amet.

* Press `M-q'. After filling once the hard newline between the
  paragraphs has been converted to a soft newline.  Filling again makes
  it into one paragraph.


In GNU Emacs 21.3.50.3 (i686-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2002-12-20 on defun.localdomain
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_US.iso88591
  locale-coding-system: iso-latin-1
  default-enable-multibyte-characters: t