MFC r227243, r233456, r248258, r248849 and r279297:

Update to upstream version 2.10

The most notable new feature is support for definition files.

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