Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Update to upstream version 2.7

The most notable new feature is support for processing multiple
files in one invocation. There is also support for more make-friendly
exit statuses.

The most notable bug fix is #line directives now include the input
file name.

Obtained from: http://dotat.at/prog/unifdef