Log Message:
Update Augeas to 1.9.0.

The changelog is too long for this commit message, go find it at
https://github.com/hercules-team/augeas/releases and
http://augeas.net/news.html.

Note that 1.8.1 included the following:
Fix error in handling escaped whitespace at the end of path expressions
(addresses CVE-2017-7555).