bug#19039: 24.3; latex-mode paragraph-separate of \pagebreak[0]

[Kevin Ryde]

In latex-mode it'd be good if \pagebreak[0] was a paragraph separator,
as for example

Blah blah         \ pagagraph
blah blah.        /
\pagebreak[0]
\begin{align}
...

An unconditional \pagebreak is already a separator, but not when an
optional arg [0] or [3] etc.

Perhaps digits and brackets like below.  Only some of the "space" "skip"
and "page" commands matched take optional args like this, but allowing
for all shouldn't hurt.

2014-11-12  Kevin Ryde  <user42_kevin@yahoo.com.au>

        * textmodes/tex-mode.el (latex-mode): In paragraph-separate allow
        optional argument [0] etc for \pagebreak[0]

tex-mode.el.diff
Description: Text Data

In GNU Emacs 24.3.1 (i586-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2014-10-17 on x86-csail-01, modified by Debian
Windowing system distributor `The X.Org Foundation', version 11.0.11601000
Configured using:
 `configure '--build' 'i586-linux-gnu' '--build' 'i586-linux-gnu'
 '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib'
 '--localstatedir=/var/lib' '--infodir=/usr/share/info'
 '--mandir=/usr/share/man' '--with-pop=yes'
 
'--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.3/site-lisp:/usr/share/emacs/site-lisp'
 '--with-crt-dir=/usr/lib/i386-linux-gnu' '--with-x=yes'
 '--with-x-toolkit=lucid' '--with-toolkit-scroll-bars' '--without-gconf'
 '--without-gsettings' 'build_alias=i586-linux-gnu' 'CFLAGS=-g -O2
 -fstack-protector-strong -Wformat -Werror=format-security -Wall'
 'LDFLAGS=-Wl,-z,relro' 'CPPFLAGS=-D_FORTIFY_SOURCE=2''

Important settings:
  value of $LANG: en_AU.utf8
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t