As described in https://wiki.php.net/vcs/gitworkflow#the_news_file it
is possible to setup a custom merge driver for NEWS so git doesnt try
to merge it. This commit sets the default merge driver for the NEWS
file to the merge driver called NEWS.
We usually don't want to touch the NEWS files when we merge and have the
news items not merged by git. Therefore we tell git to use the 'ours' strategy
for the NEWS file.
Git supports a limited $Id$ keyword expansion. This $Id$ tag is similar to
$Revision$ in SVN. We enable the $Id$ expansion only for files that use
$Revision$.
