[merge] reformat news into more standard ReST (Re: [rfc] news layout tweak)

[Ian Clatworthy]

Martin Pool wrote:
> Fixing up 1.13's news prompted me to run a few regexps to reformat
> NEWS along the lines discussed in the previous thread:

I like the new layout. We sure land this soon given the grief it
will cause merging in changes based on the old format.

bb:tweak

Remember to pull across the NEWS items since this branch started.
At a glance, that's at least:

* Jelmer's default-rich-root change
* my DirState SHA1Provider parameter change
* Robert's hook.pre_open change

> The diff is pretty noisy with the mechanical changes so I suggest you
> look at the html result.

Long live meld for reviewing changes like this!

Ian C.